The idea that the people in a territory should vote on whether to allow slavery.

They believed his anti-slavery stance threatened their way of life and the institution of slavery.

It ended the Mexican-American War in 1848, ceding the Mexican Cession (including California and much of the Southwest) to the U.S. in exchange for $15 million.

South Carolina, in December 1860.

It increased anti-slavery sentiment in the North and angered the South.

Violent conflict erupted between pro-slavery and anti-slavery settlers, showcasing the deep divisions over slavery.

They argued it was their constitutional right as sovereign states to leave the Union.

The issue of slavery in the territories, especially popular sovereignty.

Lincoln’s victory, without carrying a single Southern state, convinced many Southerners they had lost political power.

It attempted to address sectional tensions by admitting California as a free state, strengthening the Fugitive Slave Act, and allowing popular sovereignty.

It allowed popular sovereignty in Kansas and Nebraska, repealing the Missouri Compromise and leading to "Bleeding Kansas."

The annexation of Texas, disputes over the Texas-Mexico border, and U.S. desire for territorial expansion under Manifest Destiny.

It reignited tensions by raising the question of whether slavery would expand into the new territories.