What was the Kansas-Nebraska Act?

The Kansas-Nebraska Act was a federal law signed by President Franklin Pierce on May 30, 1854 that organized the Kansas and Nebraska Territories with the principle of popular sovereignty, allowing settlers in those territories to decide for themselves whether to permit slavery, thereby effectively repealing the Missouri Compromise's 36 degrees 30 minutes line that had banned slavery north of that latitude. The Act was sponsored by Senator Stephen A. Douglas of Illinois, the most prominent Northern Democrat of his generation, who chaired the Senate Committee on Territories.

Douglas had several motivations. He wanted to organize the territory to facilitate construction of a transcontinental railroad on a central route through Chicago. He wanted to assert the principle of popular sovereignty (which he sometimes called squatter sovereignty) as a way to remove the slavery question from Congress and let local settlers decide. He needed Southern support for these aims, and Southern senators demanded explicit repeal of the 36 degrees 30 minutes line that the Missouri Compromise of 1820 had drawn.

The bill divided the Nebraska Territory along the 40th parallel into two new territories: Kansas to the south and Nebraska to the north. The Act passed the Senate by 37 to 14 in March 1854 and the House by 113 to 100 in May, with Northern Democrats split.

The political consequences were enormous. The Whig Party, already weakened, fractured along sectional lines and effectively died as a national organization. Anti-Nebraska coalitions of Whigs, Free Soilers, and Democrats formed in northern states during the summer of 1854 and merged into the new Republican Party, organized in February to July 1854 in Wisconsin, Michigan, and elsewhere. Within six years a Republican, Abraham Lincoln, would be elected President. Lincoln himself reentered politics largely in response to the Kansas-Nebraska Act, delivering his Peoria speech on October 16, 1854 attacking the Act and the principle of popular sovereignty.

The Act also unleashed the violence in Kansas Territory known as Bleeding Kansas. Both proslavery and antislavery settlers rushed to Kansas to influence the territorial vote. The Lecompton constitution drafted by proslavery delegates in 1857 sought to admit Kansas as a slave state but was rejected by territorial voters and ultimately by Congress. The Topeka constitution drafted by antislavery delegates was eventually approved. Kansas was admitted as a free state on January 29, 1861, after seven southern states had already seceded.

The Supreme Court compounded the crisis by ruling in Dred Scott v. Sandford on March 6, 1857 that Congress had no power to prohibit slavery in any territory, voiding both the Missouri Compromise's original line and the Kansas-Nebraska Act's popular sovereignty principle. The Act is therefore the immediate trigger of the political realignment that produced Lincoln's election and the Civil War.