Northerners and Southerners disagreed sharply on allowing slavery in the lands acquired from Mexico in the 1840s. After intense debate and threats of Southern secession, Congress passed provisions known as the Compromise of 1850. This set of laws agreed to some of the demands made by abolitionists, Free-Soilers, and pro-slavery groups but completely satisfied none of them.
Enforcement of the Fugitive Slave Act and the Dred Scott decision enraged Northerners and strengthened the abolitionist movement during the 1850s. During the same decade, popular sovereignty brought bloodshed in Kansas. Finally, in 1859, abolitionist John Brown seized weapons at Harpers Ferry, hoping to start a slave rebellion. Frightened Southerners became shocked when some people in the North supported Brown's actions.
Antislavery and Pro-slavery strife caused the Whig Party to collapse. The new Republican Party supported Abraham Lincoln for president. Voters elected Lincoln to the presidential office in 1860. As a result, seven Southern states seceded and formed the Confederacy.
