the concept of American exceptionalism, that is, the belief that America occupies a special place among the countries of the world, and to express the conviction that Providence had foreordained the United States to spread its republican institutions across North America.

Mexican-American War, war between the United States and Mexico (April 1846–February 1848) stemming from the United States' annexation of Texas in 1845 and from a dispute over whether Texas ended at the Nueces River (Mexican claim) or the Rio Grande (U.S. claim)

when a region of a country has a stronger loyalty to its own interests than to the country as a whole.

a set of laws passed by the U.S. Congress aimed at resolving tensions between free and slave states regarding the expansion of slavery into newly acquired territories.

the ultimate political power in a government lies with the people.

divided the land immediately west of Missouri into two territories, Kansas and Nebraska.

the court ruled that enslaved people and their descendants were not U.S. citizens, could not sue in federal court, and that Congress lacked the power to prohibit slavery in U.S. territories, essentially nullifying the Missouri Compromise and further fueling the issue of slavery.

rown and his men captured prominent citizens and seized the federal armory and arsenal.

Lincoln won a popular majority in the North, and a nationwide plurality of the popular vote, but his national share of 39.7 percent of the popular vote is to date the lowest for any winner except for 1824(which was decided by a contingent election, a special vote held in the U.S. House of Representatives).

Confederate troops fired on Fort Sumter in South Carolina's Charleston Harbor. Less than 34 hours later, Union forces surrendered.