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Facts About Hoover Dam (Photo: )

Hoover Dam works as a gravity dam, which means that its foundation must rely on gravity to keep the entire structure from falling down. In fact, the technical name for this structural wonder is actually concrete arch-gravity retaining wall. The Hoover in the name refers to President Herbert Hoover. Hoover was not only an engineer himself, but also played a major part in creating the dam that would eventually be named after him when he pushed for its construction in his role as Secretary of Commerce and, later, president.

Numbers

Hoover Dam was the most expensive engineering project in U.S. history at the time of its construction between 1931 and 1935, costing $49 million. Adjusted for inflation, it would cost nearly $700 million to build in 2010, according to the book "Architectural Wonders: The World's Greatest Buildings" by Jody Thompson and Jessica Rewison. Hoover Dam rises 726 feet and is 1200 feet wide at its crest. The base of the dam is 660 feet thick, and it took 91.8 billion cubic feet of concrete to create a retaining wall that weights an estimated 6.6 million tons.

Purpose

Hoover Dam was built for several purposes, controlling floods and silt as well as irrigation. The primary purpose of the dam, however, is to generate electricity. The power plant began service on September 12, 1936. Today, the Hoover Dam electric generating plant has 17 turbines that can produce about four billion kilowatts of electricity per year, reports the U.S. Bureau of Reclamation Web site. That's enough to provide the power needs for over a million people living in the Southwestern United States, according to Thompson and Rewison.

Location

Boulder Dam was the original name of this structure, as it planned location was at Boulder Canyon. Geologists then determined that Black Canyon, about eight miles downstream, was a more suitable place to build the dam, reports the Hoover Dam Tour Company, as it offered more effective control of the river downstream.

Diverting the Colorado River

The Colorado River was diverted during constructed of Hoover Dam. Four tunnels had to be bored through both cliff faces in order to draw off water from the site. The largest of these tunnels was three miles long and had a diameter of three miles.

Lake Mead

The building of Hoover Dam created the largest manmade reservoir in the United States. Lake Mead is 110 miles long and provides 550 miles of coastline with a depth of 590 feet at its deepest. A secondary purpose of Hoover Dam has therefore been to provide a boon to tourism in the areas by creating a large site for outdoor recreation. Tourists and residents come to Lake Mead for boating, swimming and fishing.

In the Movies

The Hoover Dam has figured in a few motion pictures. The most prominent appearance was in Alfred Hitchcock's "Saboteur" in which the dam is a potential target for the titular terrorists. Miniatures were used to create the effect of Hoover Dam being destroyed in the movie "Superman." According to interviews in an article published in the Las Vegas Review-Journal, Bureau of Reclamation officials require that such movies not show the dam as having any kind of potential danger to human beings.

About the Author

Timothy Sexton's more than 10,000 articles have been published on sites ranging from USA Today to CareerAddict, from PopEater to TakeLessons.com. His writing has been referenced in books ranging from "The Reckless Life...of Marlon Brando" to "Brand New China: Advertising, Media and Commercial and from Scarface Nation to Incentive!"
Images related to Hoover Dam

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Hoover Dam works as a gravity dam, which means that its foundation must rely on gravity to keep the entire structure from falling down. In fact, the technical name for this structural wonder is actually concrete arch-gravity retaining wall. The Hoover in the name refers to President Herbert Hoover.

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SOURCE #2

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Visit America's largest home, built by George Vanderbilt. Explore the 8,000-acre beautiful and grand estate in the Blue Ridge Mountains of Asheville, NC.

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3. Biltmore House had underwater lights in its indoor swimming pool at a time when many homes were still lit with candles, oil and gas lamps. Electricity was in its formative years during the home's construction, so Biltmore architect Richard Morris Hunt decided to wire the home with both Alternating Current (AC) and Direct Current (DC), since at the time no one knew which would become the standard. The latest technology extended all the way to the Vanderbilts' 70,000 gallon swimming pool. Lights powered by low-voltage direct current lit the pool from under the water. Located along the sides, the lights were sealed inside glass globes protected by metal cages.

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Behind the Biltmore Estate: 7 Things You Didn't Know About America's Largest Home

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3. Biltmore House had underwater lights in its indoor swimming pool at a time when many homes were still lit with candles, oil and gas lamps. Electricity was in its formative years during the home's construction, so Biltmore architect Richard Morris Hunt decided to wire the home with both Alternating Current (AC) and Direct Current (DC), since at the time no one knew which would become the standard.

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Yellowstone National Park (U.S. National Park Service)

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On March 1, 1872, Yellowstone became the first national park for all to enjoy the unique hydrothermal and geologic features. Within Yellowstone’s 2.2 million acres, visitors have unparalleled opportunities to observe wildlife in an intact ecosystem, explore geothermal areas that contain about half the world’s active geysers, and view geologic wonders like the Grand Canyon of the Yellowstone River.

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Yellowstone National Park.com - Information and Travel Planner for Yellowstone

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Visitor information and planning for Yellowstone National Park. The first national park and a favorite destination to millions of visitors each year. Yellowstone has variety of wonders including geysers, wildlife and boundless scenery. Yellowstone, with over 2,000 campsites, making it a perfect destination for families of all ages

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Where is Niagara Falls ?

Collectively they are called "Niagara Falls"

Categorized by these three names: American Falls, Bridal Veil Falls, Canadian Falls

American Falls & Bridal Veil Falls

Length of brink: 1060 feet /323.08 meters

Height: 176 feet / 53.6 meters (due to rocks at the base actual fall is 70 feet/ 21.3 meters)

Volume of water: 150,000 U.S. Gallons / 567,811 Liters per second

Actual amount varies, there are two hydroelectric plants which draw water into their reservoirs prior to the Falls. Their intake greatly affects the volume of water flowing over the falls.
The amount of water being siphoned away depends on two variables. The time of year, and the time of the day. Flow is greatest over the Falls in the daytime during peak tourist season (June, July, and August). In the event of an emergency the flow can be somewhat reduced by the hydroelectric companies increasing their intake.
The Bridal Veil Falls is named for its appearance. It is located next to the American falls, separated by a small piece of land called Luna Island.

Canadian "Horseshoe" Falls

Length of brink: 2600 feet / 792.4 meters

Height: 167 feet / 50.9 meters
Volume of water: 600,000 U.S. gallons / 2,271,247 liters per second

A Brief History of the Falls. Information below graciously provided courtesy of Niagara Parks
Ice Age History of the Niagara River and Whirlpool Rapids
The Niagara River, as is the entire Great Lakes Basin of which the river is an integral part, is a legacy of the last Ice Age. 18,000 years ago southern Ontario was covered by ice sheets 2-3 kilometers thick. As they advanced southward the ice sheets gouged out the basins of the Great Lakes. Then as they melted northward for the last time they released vast quantities of meltwater into these basins. Our water is "fossil water"; less than one percent of it is renewable on an annual basis, the rest leftover from the ice sheets.

The Niagara Peninsula became free of the ice about 12,500 years ago. As the ice retreated northward, its meltwaters began to flow down through what became Lake Erie, the Niagara River and Lake Ontario, down to the St. Lawrence River, and, finally, down to the sea. There were originally 5 spillways from Lake Erie to Lake Ontario. Eventually these were reduced to one, the original Niagara Falls, at Queenston-Lewiston. From here the Falls began its steady erosion through the bedrock.

However, about 10,500 years ago, through an interplay of geological effects including alternating retreats and re-advances of the ice, and rebounding of the land when released from the intense pressure of the ice (isostatic rebound), this process was interrupted. The glacial meltwaters were rerouted through northern Ontario, bypassing the southern route. For the next 5,000 years Lake Erie remained only half the size of today, the Niagara River was reduced to about 10% of its current flow, and a much-reduced Falls stalled in the area of the Niagara Glen.

About 5,500 years ago the meltwaters were once again routed through southern Ontario, restoring the river and Falls to their full power. Then the Falls reached the Whirlpool.

It was a brief and violent encounter, a geological moment lasting only weeks, maybe even only days. In this moment the Falls of the youthful Niagara River intersected an old riverbed, one that had been buried and sealed during the last Ice Age. The Falls turned into this buried gorge, tore out the glacial debris that filled it, and scoured the old river bottom clean. It was probably not a falls at all now but a huge, churning rapids. When it was all over it left behind a 90-degree turn in the river we know today as the Whirlpool, and North America's largest series of standing waves we know today as the Whirlpool Rapids.

The Falls then re-established at about the area of the Whirlpool Rapids Bridge upriver to our right, and resumed carving its way through solid rock to its present location.

Straddling the Canadian-United States International Border and both in the Province of Ontario and the State of New York, Niagara Falls attracts some 12 Million tourists to her majestic awesome beauty each year.

The Niagara is a fairly young river, only 12,000 years old!, a microsecond in geological time. The Niagara Escarpment, which was created by erosion is much older. The glaciers pressed down on the land during the last ice age and laid down layers of sediment, then the slow process of erosion of ice and water ate at the surface of the escarpment
The mighty river plunges over a cliff of dolostone and shale. Niagara Falls is the second largest falls on the globe next to Victoria Falls in southern Africa.

One fifth of all the fresh water in the world lies in the four Upper Great Lakes-Michigan, Huron,Superior and Erie. All the outflow empties into the Niagara river and eventually cascades over the falls.
At the bottom of the falls, the water travels 15 miles over many gorges until it reaches the fifth Great Lake-Ontario. The land between the lakes does not slope at an even grade, but forms a spectacular drop approximately the same height as a 20 story building and this is known as the "Niagara Escarpment" Two billion years ago it was buried under a blanket of ice.

As the years passed, the process of erosion took place, (and still does) five distinct 'gorges' were formed-Lewiston Brange Gorge, Old Narrow Gorge, Upper & Lower Great Gorges and the Whirlpool Narrow Gorge.
Approximately 500 years ago the river encountered an obstacle that caused it to 'split into two channels', thus Goat Island was formed named after John Stedman whose goat herds froze to death in the winter of 1780). This was the original sediment left from a vanished Lake Tonawanda (an Indian name).
On the eastern part of the island, the American Falls took shape, the Horseshoe Falls, is on the western side, where the river angles some 90 degrees. The water flow on the American side of the falls is much less in strength because of Goat Island, whereas Horseshoe Falls has no obstruction to divert it. It should be noted that a third much narrower falls exists. Over the years these falls have been called at different times; Luna Falls, Iris Falls and is currently named Bridal Veil Falls.
Man has not been able to completely control the flow of the water over the falls, even modern engineers have tried. Much of the water today is fed through underground channels and pipes to nearby hydro electric power stations.

Do the Falls Freeze over in the Winter?
Yes and No...... We'll try to explain
The tremendous volume of water never stops flowing, However, the falling water and mist create ice formations along the banks of the falls and river. This can result in mounds of ice as thick as fifty feet. If the winter is cold for long enough, the ice will completely stretch across the river and form what is known as the "ice bridge". This ice bridge can extend for several miles down river until it reaches the area known as the lower rapids.

Until 1912,visitors were allowed to actually walk out on the ice bridge and view the Falls from below. February 24th of 1888 the local newspaper reported that at least 20,000 people watched or tobogganed on the ice. Shanties selling liquor, photographs and curiosities abounded. On February 4th 1912 the ice bridge broke up and three tourists lives were lost.

There can also be a great deal of "mini-icebergs" which flow down the Niagara River from frozen Lake Erie. The flow of ice has been reduced considerably by the yearly installation of the "ice-boom" on Lake Erie. The ice-boom is a long floating chain (2miles- 3.2 KM) of steel floats strung across the Niagara River from Buffalo New York to Fort Erie Ontario. It is set in place during the month of December and removed during the month of March or April. It is maintained by the New York State Power Authority. The ice boom helps prevent the ice from clogging the river and most importantly the hydroelectric companies water intakes.

Spring Ice flowing underneath the North Grand Island Bridge

HOWEVER.... The flow of water was stopped completely over both falls on March 29th 1848 due to an ice jam in the upper river for several hours. This is the only known time to have occurred. The Falls did not actually freeze over, but the flow was stopped to the point where people actually walked out and recovered artifacts from the riverbed!
Interesting facts about Niagara Falls
The flow over the American Falls was stopped completely for several months in 1969. The idea was to determine the feasibility of removing the large amount of loose rock from the base of the falls to enhance its appearance. In the end the final decision was that the expense would be too great.

The word "Niagara" is derived from the Iroquois Indian word "Onguiaahra" meaning "the strait"
There is an international boundary between the United States and Canada.
Before the invention of film, tourists would sketch pictures of the Falls.
The flow was also halted over both falls on March 30th 1848 due to an ice jam in the upper river.
The movies Niagara and Superman were filmed in part at the Falls.
In the past ten years, two daredevils lost their lives trying to conquer Niagara.
In the evenings, intense spotlights bathe the falls with different shades of color.
The first person to go over the Falls in a barrel and survive was a 63 year old female schoolteacher.
High wire tightrope acts used to be performed across the river. Most notably was "Blondin" who once actually carried his manager across on his back, stopping midway to rest !
The Falls make a tremendous sound as the water goes over and lands at the bottom.
Twenty percent of the worlds freshwater lies in the Great Lakes, and most flows over Niagara Falls.

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Where is Niagara Falls ? Collectively they are called "Niagara Falls" Categorized by these three names: American Falls, Bridal Veil Falls, Canadian Falls American Falls & Bridal Veil Falls Length of brink: 1060 feet /323.08 meters Height: 176 feet / 53.6 meters (due to rocks at the base actual fall is 70 feet/ 21.3 meters) Volume of water: 150,000 U.S.

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History of Niagara Falls | Niagara Falls State Park

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Get to know America's oldest state park. With historical details and fascinating facts, you can learn about Niagara Falls State Park before you arrive.

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SOURCE #2

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Golden Gate Bridge - Facts & Summary - HISTORY.com

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Find out more about the history of Golden Gate Bridge, including videos, interesting articles, pictures, historical features and more. Get all the facts on HISTORY.com

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The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the one-mile-wide (1.6 km) strait connecting San Francisco Bay and the Pacific Ocean. The structure links the U.S. city of San Francisco, California-the northern tip of the San Francisco Peninsula-to Marin County, carrying both U.S. Route 101 and California State Route 1 across the strait. It also carries pedestrian and bicycle traffic, and is designated as part of U.S. Bicycle Route 95. Recognized by the American Society of Civil Engineers as one of the Wonders of the Modern World, the bridge is one of the most internationally recognized symbols of San Francisco and California.

The idea of a fixed link between San Francisco and Marin had gained increasing popularity during the late 19th century, but it was not until the early 20th century that such a link became feasible. Joseph Strauss served as chief engineer for the project, with Leon Moisseiff, Irving Morrow and Charles Ellis making significant contributions to its design. The bridge opened to the public in 1937 and has undergone various retrofits and other improvement projects in the decades since.

The Golden Gate Bridge is described in Frommer's travel guide as "possibly the most beautiful, certainly the most photographed, bridge in the world." At the time of its opening in 1937, it was both the longest and the tallest suspension bridge in the world, titles it held until 1964 and 1998 respectively. Its main span is 4,200 feet (1,280 m) and its total height is 746 feet (227 m).

Before the bridge was built, the only practical short route between San Francisco and what is now Marin County was by boat across a section of San Francisco Bay. A ferry service began as early as 1820, with a regularly scheduled service beginning in the 1840s for the purpose of transporting water to San Francisco.

In 1867, the Sausalito Land and Ferry Company opened. In 1920, the service was taken over by the Golden Gate Ferry Company, which merged in 1929 with the ferry system of the Southern Pacific Railroad, becoming the Southern Pacific-Golden Gate Ferries, Ltd., the largest ferry operation in the world. Once for railroad passengers and customers only, Southern Pacific's automobile ferries became very profitable and important to the regional economy. The ferry crossing between the Hyde Street Pier in San Francisco and Sausalito Ferry Terminal in Marin County took approximately 20 minutes and cost $1.00 per vehicle prior to 1937, when the price was reduced to compete with the new bridge. The trip from the San Francisco Ferry Building took 27 minutes.

Golden Gate with Fort Point in foreground, c. 1891

Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took hold was made in a 1916 San Francisco Bulletin article by former engineering student James Wilkins. San Francisco's City Engineer estimated the cost at $100 million (equivalent to $2.7 billion today), and impractical for the time. He asked bridge engineers whether it could be built for less. One who responded, Joseph Strauss, was an ambitious engineer and poet who had, for his graduate thesis, designed a 55-mile-long (89 km) railroad bridge across the Bering Strait. At the time, Strauss had completed some 400 drawbridges-most of which were inland-and nothing on the scale of the new project. Strauss's initial drawings were for a massive cantilever on each side of the strait, connected by a central suspension segment, which Strauss promised could be built for $17 million (equivalent to $457 million today).

A suspension-bridge design was chosen, using recent advances in bridge design and metallurgy.

Strauss spent more than a decade drumming up support in Northern California. The bridge faced opposition, including litigation, from many sources. The Department of War was concerned that the bridge would interfere with ship traffic. The US Navy feared that a ship collision or sabotage to the bridge could block the entrance to one of its main harbors. Unions demanded guarantees that local workers would be favored for construction jobs. Southern Pacific Railroad, one of the most powerful business interests in California, opposed the bridge as competition to its ferry fleet and filed a lawsuit against the project, leading to a mass boycott of the ferry service.

In May 1924, Colonel Herbert Deakyne held the second hearing on the Bridge on behalf of the Secretary of War in a request to use federal land for construction. Deakyne, on behalf of the Secretary of War, approved the transfer of land needed for the bridge structure and leading roads to the "Bridging the Golden Gate Association" and both San Francisco County and Marin County, pending further bridge plans by Strauss. Another ally was the fledgling automobile industry, which supported the development of roads and bridges to increase demand for automobiles.

The bridge's name was first used when the project was initially discussed in 1917 by M.M. O'Shaughnessy, city engineer of San Francisco, and Strauss. The name became official with the passage of the Golden Gate Bridge and Highway District Act by the state legislature in 1923, creating a special district to design, build and finance the bridge. San Francisco and most of the counties along the North Coast of California joined the Golden Gate Bridge District, with the exception being Humboldt County, whose residents opposed the bridge's construction and the traffic it would generate.

South tower seen from walkway, with Art Deco elements

Strauss was the chief engineer in charge of the overall design and construction of the bridge project. However, because he had little understanding or experience with cable-suspension designs, responsibility for much of the engineering and architecture fell on other experts. Strauss's initial design proposal (two double cantilever spans linked by a central suspension segment) was unacceptable from a visual standpoint. The final graceful suspension design was conceived and championed by Leon Moisseiff, the engineer of the Manhattan Bridge in New York City.

Irving Morrow, a relatively unknown residential architect, designed the overall shape of the bridge towers, the lighting scheme, and Art Deco elements, such as the tower decorations, streetlights, railing, and walkways. The famous International Orange color was Morrow's personal selection, winning out over other possibilities, including the US Navy's suggestion that it be painted with black and yellow stripes to ensure visibility by passing ships.

Senior engineer Charles Alton Ellis, collaborating remotely with Moisseiff, was the principal engineer of the project. Moisseiff produced the basic structural design, introducing his "deflection theory" by which a thin, flexible roadway would flex in the wind, greatly reducing stress by transmitting forces via suspension cables to the bridge towers. Although the Golden Gate Bridge design has proved sound, a later Moisseiff design, the original Tacoma Narrows Bridge, collapsed in a strong windstorm soon after it was completed, because of an unexpected aeroelastic flutter. Ellis was also tasked with designing a "bridge within a bridge" in the southern abutment, to avoid the need to demolish Fort Point, a pre-Civil War masonry fortification viewed, even then, as worthy of historic preservation. He penned a graceful steel arch spanning the fort and carrying the roadway to the bridge's southern anchorage.

The Golden Gate Bridge and Highway District, authorized by an act of the California Legislature, was incorporated in 1928 as the official entity to design, construct, and finance the Golden Gate Bridge. However, after the Wall Street Crash of 1929, the District was unable to raise the construction funds, so it lobbied for a $30 million bond measure (equivalent to $511 million today). The bonds were approved in November 1930, by votes in the counties affected by the bridge. The construction budget at the time of approval was $27 million ($473 million today). However, the District was unable to sell the bonds until 1932, when Amadeo Giannini, the founder of San Francisco-based Bank of America, agreed on behalf of his bank to buy the entire issue in order to help the local economy.

Construction began on January 5, 1933. The project cost more than $35 million ($550 million in 2021 dollars), and was completed ahead of schedule and $1.3 million under budget (equivalent to $27.7 million today). The Golden Gate Bridge construction project was carried out by the McClintic-Marshall Construction Co., a subsidiary of Bethlehem Steel Corporation founded by Howard H. McClintic and Charles D. Marshall, both of Lehigh University.

An original rivet replaced during the seismic retrofit after the 1989 Loma Prieta earthquake. A total of 1.2 million steel rivets hold the bridge's two towers together.

Strauss remained head of the project, overseeing day-to-day construction and making some groundbreaking contributions. A graduate of the University of Cincinnati, he placed a brick from his alma mater's demolished McMicken Hall in the south anchorage before the concrete was poured.

Strauss also innovated the use of movable safety netting beneath the men working, which saved many lives. Nineteen men saved by the nets over the course of the project formed the Half Way to Hell Club. Nonetheless eleven men were killed in falls, ten on February 17, 1937, when a scaffold (secured by undersized bolts) with twelve men on it fell into and broke through the safety net; two of the twelve survived the 200-foot (61 m) fall into the water.

The bridge opened May 27, 1937.

The Round House Café diner was then included in the southeastern end of the Golden Gate Bridge, adjacent to the tourist plaza which was renovated in 2012. The Round House Café, an Art Deco design by Alfred Finnila completed in 1938, has been popular throughout the years as a starting point for various commercial tours of the bridge and an unofficial gift shop. The diner was renovated in 2012 and the gift shop was then removed as a new, official gift shop has been included in the adjacent plaza.

During the bridge work, the Assistant Civil Engineer of California Alfred Finnila had overseen the entire iron work of the bridge as well as half of the bridge's road work.

Contributors

Plaque of the major contributors to the Golden Gate Bridge lists contractors, engineering-staff, directors and officers:

Contractors

Foundations - Pacific Bridge Company

Anchorages - Barrett & Hilp

Structural steel - Main span - Bethlehem Steel Company Incorporated

Approach steel - J.H. Pomeroy & Company Incorporated - Raymond Concrete Pile Company

Cables - John A. Roebling's Sons Company

Electrical work - Alta Electric and Mechanical Company Incorporated

Bridge deck - Pacific Bridge Company

Presidio Approach Roads and Viaducts - Easton & Smith

Toll Plaza - Barrett & Hilp

Engineering staff

Chief engineer - Joseph B. Strauss

Principal assistant engineer - Clifford E. Paine

Resident engineer - Russell Cone

Assistant engineer - Charles Clarahan Jr., Dwight N. Wetherell

Consulting engineer - O.H. Ammann, Charles Derleth Jr., Leon S. Moisseiff

Consulting traffic engineer - Sydney W. Taylor, Jr.

Consulting architect - Irving F. Morrow

Consulting geologist - Andrew C. Lawson, Allan E. Sedgwick

Directors

San Francisco - William P. Filmer, Richard J. Welch, Warren Shannon, Hugo D. Newhouse, Arthur M. Brown, Jr., John P. McLaughlin, William D. Hadeler, C.A. Henry, Francis V. Keesling, William P. Stanton, George T. Cameron

Marin County - Robert H. Trumbull, Harry Lutgens

Napa County - Thomas Maxwell

Sonoma County - Frank P. Doyle, Joseph A. McMinn

Mendocino County - A. R. O'Brien

Del Norte County - Henry Westbrook, Jr., Milton M. McVay

Officers

President - William P. Filmer

Vice President - Robert H. Trumbull

General manager - James Reed, Alan McDonald

Chief engineer - Joseph B. Strauss

Secretary - W. W. Felt, Jr.

Auditor - Roy S. West, John R. Ruckstell

Attorney - George H. Harlan

On December 1, 1951, a windstorm revealed swaying and rolling instabilities of the bridge, resulting in its closure. In 1953 and 1954, the bridge was retrofitted with lateral and diagonal bracing that connected the lower chords of the two side trusses. This bracing stiffened the bridge deck in torsion so that it would better resist the types of twisting that had destroyed the Tacoma Narrows Bridge in 1940.

Bridge deck replacement (1982-1986)

The original bridge used a concrete deck. Salt carried by fog or mist reached the rebar, causing corrosion and concrete spalling. From 1982 to 1986, the original bridge deck, in 747 sections, was systematically replaced with a 40% lighter, and stronger, steel orthotropic deck panels, over 401 nights without closing the roadway completely to traffic. The roadway was also widened by two feet, resulting in outside curb lane width of 11 feet, instead of 10 feet for the inside lanes. This deck replacement was the bridge's greatest engineering project since it was built and cost over $68 million.

Opening festivities, and 50th and 75th anniversaries

The Golden Gate Bridge and Fort Point

The bridge-opening celebration in 1937 began on May 27 and lasted for one week. The day before vehicle traffic was allowed, 200,000 people crossed either on foot or on roller skates. On opening day, Mayor Angelo Rossi and other officials rode the ferry to Marin, then crossed the bridge in a motorcade past three ceremonial "barriers," the last a blockade of beauty queens who required Joseph Strauss to present the bridge to the Highway District before allowing him to pass. An official song, " There's a Silver Moon on the Golden Gate," was chosen to commemorate the event. Strauss wrote a poem that is now on the Golden Gate Bridge entitled "The Mighty Task is Done." The next day, President Franklin D. Roosevelt pushed a button in Washington, D.C. signaling the official start of vehicle traffic over the Bridge at noon. Weeks of civil and cultural activities called "the Fiesta" followed. A statue of Strauss was moved in 1955 to a site near the bridge.

As part of the fiftieth anniversary celebration in 1987, the Golden Gate Bridge district again closed the bridge to automobile traffic and allowed pedestrians to cross it on May 24. This Sunday morning celebration attracted 750,000 to 1,000,000 people, and ineffective crowd control meant the bridge became congested with roughly 300,000 people, causing the center span of the bridge to flatten out under the weight. Although the bridge is designed to flex in that way under heavy loads, and was estimated not to have exceeded 40% of the yielding stress of the suspension cables, bridge officials stated that uncontrolled pedestrian access was not being considered as part of the 75th anniversary on Sunday, May 27, 2012, because of the additional law enforcement costs required "since 9/11."

Opening of the Golden Gate Bridge

Official invitation to the opening of the bridge. This copy was sent to the City of Seattle.

On the 50th anniversary of the Golden Gate Bridge in 1987, individuals and organizations were invited to buy a commemorative brick to fund the 50th anniversary celebration. Those bricks were installed on the ground creating a brick promenade. Its location is shown on the map.

More than 7,500 donors responded, personalizing their brick with inscriptions and tributes.

Unfortunately, 25 years later, for the upcoming 75th of the Golden Gate Bridge, the need for a DDA compliant area, as the slope was too steep, implied remodeling the whole promenade. Doing so, and contractors being unable to properly take bricks out one by one, the brick promenade was demolished and the contributors were unable to get their bricks back.

However, to honor and respect their contributions, all the donors' names and the inscriptions they had chosen for their bricks have been preserved and written on panels.

The panels are located inside the "Equator Coffees", on its rounded walls. The names and inscriptions are listed in the alphabetical order, to make them easier to read and find.

This website has been keeping a maps view of the original brick promenade and the database of all donors' names and inscriptions, to help find and locate them on the original layout. As of October 2022, the website is currently down.

Until 1964, the Golden Gate Bridge had the longest suspension bridge main span in the world, at 4,200 feet (1,300 m). Since 1964 its main span length has been surpassed by seventeen bridges; it now has the second-longest main span in the Americas, after the Verrazzano-Narrows Bridge in New York City. The total length of the Golden Gate Bridge from abutment to abutment is 8,981 feet (2,737 m).

The Golden Gate Bridge's clearance above high water averages 220 feet (67 m) while its towers, at 746 feet (227 m) above the water, were the world's tallest on a suspension bridge until 1993 when it was surpassed by the Mezcala Bridge, in Mexico.

The weight of the roadway is hung from 250 pairs of vertical suspender ropes, which are attached to two main cables. The main cables pass over the two main towers and are fixed in concrete at each end. Each cable is made of 27,572 strands of wire. The total length of galvanized steel wire used to fabricate both main cables is estimated to be 80,000 miles (130,000 km). Each of the bridge's two towers has approximately 600,000 rivets.

In the 1960s, when the Bay Area Rapid Transit system (BART) was being planned, the engineering community had conflicting opinions about the feasibility of running train tracks north to Marin County over the bridge. In June 1961, consultants hired by BART completed a study that determined the bridge's suspension section was capable of supporting service on a new lower deck. In July 1961, one of the bridge's consulting engineers, Clifford Paine, disagreed with their conclusion. In January 1962, due to more conflicting reports on feasibility, the bridge's board of directors appointed an engineering review board to analyze all the reports. The review board's report, released in April 1962, concluded that running BART on the bridge was not advisable.

Aesthetics was the foremost reason why the first design of Joseph Strauss was rejected. Upon re-submission of his bridge construction plan, he added details, such as lighting, to outline the bridge's cables and towers. In 1999, it was ranked fifth on the List of America's Favorite Architecture by the American Institute of Architects.

The color of the bridge is officially an orange vermilion called international orange. The color was selected by consulting architect Irving Morrow because it complements the natural surroundings and enhances the bridge's visibility in fog.

The bridge was originally painted with red lead primer and a lead-based topcoat, which was touched up as required. In the mid-1960s, a program was started to improve corrosion protection by stripping the original paint and repainting the bridge with zinc silicate primer and vinyl topcoats. Since 1990, acrylic topcoats have been used instead for air-quality reasons. The program was completed in 1995 and it is now maintained by 38 painters who touch up the paintwork where it becomes seriously corroded. The ongoing maintenance task of painting the bridge is continuous.

Testing the newly installed movable barrier

Most maps and signage mark the bridge as part of the concurrency between U.S. Route 101 and California State Route 1. Although part of the National Highway System, the bridge is not officially part of California's Highway System. For example, under the California Streets and Highways Code § 401, Route 101 ends at "the approach to the Golden Gate Bridge" and then resumes at "a point in Marin County opposite San Francisco". The Golden Gate Bridge, Highway and Transportation District has jurisdiction over the segment of highway that crosses the bridge instead of the California Department of Transportation (Caltrans).

The movable median barrier between the lanes is moved several times daily to conform to traffic patterns. On weekday mornings, traffic flows mostly southbound into the city, so four of the six lanes run southbound. Conversely, on weekday afternoons, four lanes run northbound. During off-peak periods and weekends, traffic is split with three lanes in each direction.

From 1968 to 2015, opposing traffic was separated by small, plastic pylons; during that time, there were 16 fatalities resulting from 128 head-on collisions. To improve safety, the speed limit on the Golden Gate Bridge was reduced from 50 to 45 mph (80 to 72 km/h) on October 1, 1983. Although there had been discussion concerning the installation of a movable barrier since the 1980s, only in March 2005 did the Bridge Board of Directors commit to finding funding to complete the $2 million study required prior to the installation of a movable median barrier. Installation of the resulting barrier was completed on January 11, 2015, following a closure of 45.5 hours to private vehicle traffic, the longest in the bridge's history. The new barrier system, including the zipper trucks, cost approximately $30.3 million to purchase and install.

The bridge carries about 112,000 vehicles per day according to the Golden Gate Bridge Highway and Transportation District.

Looking north with traffic and current flow into the bay with sailboats

The bridge is popular with pedestrians and bicyclists, and was built with walkways on either side of the six vehicle traffic lanes. Initially, they were separated from the traffic lanes by only a metal curb, but railings between the walkways and the traffic lanes were added in 2003, primarily as a measure to prevent bicyclists from falling into the roadway. The bridge was designated as part of U.S. Bicycle Route 95 in 2021.

The main walkway is on the eastern side, and is open for use by both pedestrians and bicycles in the morning to mid-afternoon during weekdays (5:00 a.m. to 3:30 p.m.), and to pedestrians only for the remaining daylight hours (until 6:00 p.m., or 9:00 p.m. during DST). The eastern walkway is reserved for pedestrians on weekends (5:00 a.m. to 6:00 p.m., or 9:00 p.m. during DST), and is open exclusively to bicyclists in the evening and overnight, when it is closed to pedestrians. The western walkway is open only for bicyclists and only during the hours when they are not allowed on the eastern walkway.

Bus service across the bridge is provided by two public transportation agencies: San Francisco Muni and Golden Gate Transit. Muni offers Saturday and Sunday service on the Marin Headlands Express bus line, and Golden Gate Transit runs numerous bus lines throughout the week. The southern end of the bridge, near the toll plaza and parking lot, is also accessible daily from 5:30 a.m. to midnight by Muni line 28. The Marin Airporter, a private company, also offers service across the bridge between Marin County and San Francisco International Airport.

A visitor center and gift shop, originally called the "Bridge Pavilion" (since renamed the "Golden Gate Bridge Welcome Center"), is located on the San Francisco side of the bridge, adjacent to the southeast parking lot. It opened in 2012, in time for the bridge's 75th-anniversary celebration. A cafe, outdoor exhibits, and restroom facilities are located nearby. On the Marin side of the bridge, only accessible from the northbound lanes, is the H. Dana Bower Rest Area and Vista Point, named after the first landscape architect for the California Division of Highways.

Lands and waters under and around the bridge are homes to varieties of wildlife such as bobcats, harbor seals, and sea lions. Three species of cetaceans (whales) that had been absent in the area for many years have shown recent[when? ] recoveries/(re)colonizations in the vicinity of the bridge; researchers studying them have encouraged stronger protections and recommended that the public watch them from the bridge or from land, or use a local whale watching operator.

Current toll rates

Tolls are only collected from southbound traffic at the toll plaza on the San Francisco side of the bridge. All-electronic tolling has been in effect since 2013, and drivers may either pay using the FasTrak electronic toll collection device, using the license plate tolling program, or via a one time payment online. Effective July 1, 2023, the regular toll rate for passenger cars is $9, with FasTrak users paying a discounted toll of $8.75. During peak traffic hours, carpool vehicles carrying three or more people, or motorcycles may pay a discounted toll of $6.75 if they have FasTrak and use the designated carpool lane. Drivers must pay within 48 hours after crossing the bridge or they will be sent a toll violation invoice. The toll violation penalty is $9.75, and additional fees will be added if it is not paid within 21 days.

Historical toll rates

When the Golden Gate Bridge opened in 1937, the toll was 50cents per car (equivalent to $10.18 in 2022), collected in each direction. In 1950 it was reduced to 40cents each way ($4.87 in 2022), then lowered to 25cents in 1955 ($2.73 in 2022). In 1968, the bridge was converted to only collect tolls from southbound traffic, with the toll amount reset back to 50cents ($4.21 in 2022).

The bridge began accepting tolls via the FasTrak electronic toll collection system in 2002, with $4 tolls for FasTrak users and $5 for those paying cash (equivalent to $6.51 and $8.14 respectively in 2022). In November 2006, the Golden Gate Bridge, Highway and Transportation District recommended a corporate sponsorship program for the bridge to address its operating deficit, projected at $80 million over five years. The District promised that the proposal, which it called a "partnership program", would not include changing the name of the bridge or placing advertising on the bridge itself. In October 2007, the Board unanimously voted to discontinue the proposal and seek additional revenue through other means, most likely a toll increase. The District later increased the toll amounts in 2008 to $5 for FasTrak users and $6 to those paying cash (equivalent to $6.8 and $8.16 respectively in 2022).

In an effort to save $19.2 million over the following 10 years, the Golden Gate District voted in January 2011 to eliminate all toll takers by 2012 and use only open road tolling. Subsequently, this was delayed and toll taker elimination occurred in March 2013. The cost savings have been revised to $19 million over an eight-year period. In addition to FasTrak, the Golden Gate Transportation District implemented the use of license plate tolling (branded as "Pay-by-Plate"), and also a one-time payment system for drivers to pay before or after their trip on the bridge. Twenty-eight positions were eliminated as part of this plan.

On April 7, 2014, the toll for users of FasTrak was increased from $5 to $6 (equivalent to $7.42 in 2022), while the toll for drivers using either the license plate tolling or the one time payment system was raised from $6 to $7 (equivalent to $8.65 in 2022). Bicycle, pedestrian, and northbound motor vehicle traffic remain toll free. For vehicles with more than two axles, the toll rate was $7 per axle for those using license plate tolling or the one time payment system, and $6 per axle for FasTrak users. During peak traffic hours, carpool vehicles carrying two or more people and motorcycles paid a discounted toll of $4 (equivalent to $4.94 in 2022); drivers must have had Fastrak to take advantage of this carpool rate. The Golden Gate Transportation District then increased the tolls by 25cents in July 2015, and then by another 25cents each of the next three years.

In March 2019, the Golden Gate Transportation District approved a plan to implement 35-cent annual toll increases through 2023, except for the toll-by-plate program which will increase by 20cents per year.

In March 2008, the Golden Gate Bridge District board approved a resolution to start congestion pricing at the Golden Gate Bridge, charging higher tolls during the peak hours, but rising and falling depending on traffic levels. This decision allowed the Bay Area to meet the federal requirement to receive $158 million in federal transportation funds from USDOT Urban Partnership grant. As a condition of the grant, the congestion toll was to be in place by September 2009.

In August 2008, transportation officials ended the congestion pricing program in favor of varying rates for metered parking along the route to the bridge including on Lombard Street and Van Ness Avenue.

The Golden Gate Bridge is the most used suicide site in the world. The deck is about 245 feet (75 m) above the water. After a fall of four seconds, jumpers hit the water at around 75 mph (120 km/h; 30 m/s). Most die from impact trauma. About 5% survive the initial impact but generally drown or die of hypothermia in the cold water.

After years of debate and an estimated more than 1,500 deaths, suicide barriers, consisting of a stainless steel net extending 20 feet from the bridge and supported by structural steel 20 feet under the walkway, began to be installed in April 2017. Construction was first estimated to take approximately four years at a cost of over $200 million. In December 2019, it was reported that construction of the suicide prevention net had fallen two years behind schedule because the lead contractor, Shimmick Construction Co., had been sold in 2017, leading to the slowdown of several existing projects. As of December 2019, the completion date for the Golden Gate Bridge net was set for 2023.

The Golden Gate Bridge was designed to safely withstand winds of up to 68 mph (109 km/h). Until 2008, the bridge was closed because of weather conditions only three times: on December 1, 1951, because of gusts of 69 mph (111 km/h); on December 23, 1982, because of winds of 70 mph (113 km/h); and on December 3, 1983, because of wind gusts of 75 mph (121 km/h). An anemometer placed midway between the two towers on the west side of the bridge has been used to measure wind speeds. Another anemometer was placed on one of the towers.

As part of the retrofitting of the bridge and installation of the suicide barrier, starting in 2019 the railings on the west side of the pedestrian walkway were replaced with thinner, more flexible slats in order to improve the bridge's aerodynamic tolerance of high wind to 100 mph (161 km/h). Starting in June 2020, reports were received of a loud hum, heard across San Francisco and Marin County, produced by the new railing slats when a strong west wind was blowing. The sound had been predicted from wind tunnel tests, but not included in the environmental impact report; ways of ameliorating it are being considered. An independent engineering analysis of a 2020 sound recording of the tones concludes that the singing noise comprises a variety of Aeolian tones (the sound produced by air flowing past a sharp edge), arising in this case from the ambient wind blowing across metal slats of the newly installed sidewalk railings. The tones observed were frequencies of 354, 398, 439 and 481 Hz, corresponding to the musical notes F ₄, G ₄, A ₄, and B ₄; these notes form an F Lydian Tetrachord.

South approach sub-structure with seismic isolators (short black cylinders) added as part of the Seismic Retrofit Construction Project

Modern knowledge of the effect of earthquakes on structures led to a program to retrofit the Golden Gate to better resist seismic events. The proximity of the bridge to the San Andreas Fault places it at risk for a significant earthquake. Once thought to have been able to withstand any magnitude of foreseeable earthquake, the bridge was actually vulnerable to complete structural failure (i.e., collapse) triggered by the failure of supports on the 320-foot (98 m) arch over Fort Point. A $392 million program was initiated to improve the structure's ability to withstand such an event with only minimal (repairable) damage. A custom-built electro-hydraulic synchronous lift system for construction of temporary support towers and a series of intricate lifts, transferring the loads from the existing bridge onto the temporary supports, were completed with engineers from Balfour Beatty and Enerpac, without disrupting day-to-day commuter traffic. Although the retrofit was initially planned to be completed in 2012, as of May 2017 it was expected to take several more years.

The former elevated approach to the Golden Gate Bridge through the San Francisco Presidio, known as Doyle Drive, dated to 1933 and was named after Frank P. Doyle. Doyle, the president of the Exchange Bank in Santa Rosa and son of the bank's founder, was the man who, more than any other person, made it possible to build the Golden Gate Bridge. The highway carried about 91,000 vehicles each weekday between downtown San Francisco and the North Bay and points north. The road was deemed "vulnerable to earthquake damage", had a problematic 4-lane design, and lacked shoulders; a San Francisco County Transportation Authority study recommended that it be replaced. Construction on the $1 billion replacement, temporarily known as the Presidio Parkway, began in December 2009. The elevated Doyle Drive was demolished on the weekend of April 27-30, 2012, and traffic used a part of the partially completed Presidio Parkway, until it was switched onto the finished Presidio Parkway on the weekend of July 9-12, 2015. As of May 2012, an official at Caltrans said there is no plan to permanently rename the portion known as Doyle Drive.

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# data[].attributes.attachment_link.description
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the one-mile-wide (1.6 km) strait connecting San Francisco Bay and the Pacific Ocean. The structure links the U.S. city of San Francisco, California-the northern tip of the San Francisco Peninsula-to Marin County, carrying both U.S.