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The first steps toward inventing radio involved discovering electromagnetic waves and their potential. Hans Christian Oersted was the first to proclaim that a magnetic field is created around a wire that has a current running through it.

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English physicist Michael Faraday confirmed Oersted's theory, and established the principle of electromagnetic induction.

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James Clerk Maxwell, an experimental physics professor at Cambridge University, published a theoretical paper stating that electromagnetic currents could be perceived at a distance. Maxwell also boldly postulated that such waves travelled at the speed of light.

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German physicist Heinrich Hertz tested Maxwell's theory. He succeeded in producing electromagnetic waves, and confirmed Maxwell's prediction about their speed.

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Not long after, Guglielmo Marconi, an Italian inventor, brought electromagnetic waves out of the laboratory and into the world. He began with short-distance broadcasts in his own back yard. In September, 1899, he astounded the world by telegraphing the results of the America's Cup yacht races from a ship at sea to a land-based station in New York.

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For a time, wireless broadcasts were limited to coded dots and dashes. But on December 24, 1906, Canadian-born physicist Reginald Fessenden changed that by sending the first long-distance transmission of human voice and music from his station at Brant Rock, Massachusetts. His signal was received as far away as Norfolk, Virginia. The stage for commercial voice and music broadcasts was set.

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A steady stream of inventions pushed radio forward. In 1907, American inventor Lee De Forest introduced his patented Audion signal detector--which allowed radio frequency signals to be amplified dramatically.

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The public demand for radio grew exponentially. Entertainment broadcasting began in about 1910, and included De Forest's own program, which he aired from the Metropolitan Opera House in New York City.

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The radio was primarily used to contact ships that were out at sea. Radio communications were not very clear, so operators typically relied on the use of Morse code messages.

During the war, the military used it almost exclusively and it became an invaluable tool in sending and receiving messages to the armed forces in real time, without the need for a physical messenger.

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An entertainment broadcasting venture based in Wilkinsburg, Pennsylvania, became the first commercial radio station, KDKA, in 1920.

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It was AT&T that, in 1923, released the first radio advertisement. In the late 20s, CBS and NBC were created in response to AT&T being the sole station with rights to toll broadcasting.

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In Britain, radio broadcasts began in 1922 with the British Broadcasting Company, or BBC, in London. At this point the radio and the BBC became the leading source of information for the public.

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The period between the late 1920s and the early 1950s is considered the Golden Age of Radio, in which comedies, dramas, variety shows, game shows, and popular music shows drew millions of listeners across America. But in the 1950s, with the introduction of television, the Golden Age faded.

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While radio had previously been a source of entertainment in the form of serial programs, after the war it began to focus more on playing the music of the time. The "Top-40" in music became popular during this period and the target audience went from families to pre-teens up to adults in their mid-thirties. Music and radio continued to rise in popularity until they became synonymous with one another. FM radio stations began to overtake the original AM stations, and new forms of music, such as rock and roll, began to emerge.

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Already more than 100 years old, radio is still a powerful force in American life. According to a 1998 Arbitron report, over 95 percent of Americans listen to radio at least once a week.