Kansas–Nebraska Act

The Kansas–Nebraska Act of 1854 (10 Stat. 277) was a territorial organic act that created the territories of Kansas and Nebraska. It was drafted by Democratic Senator Stephen A. Douglas, passed by the 33rd United States Congress, and signed into law by President Franklin Pierce. Douglas introduced the bill intending to open up new lands to develop and facilitate the construction of a transcontinental railroad. However, the Kansas–Nebraska Act effectively repealed the Missouri Compromise of 1820, stoking national tensions over slavery and contributing to a series of armed conflicts known as "Bleeding Kansas".

The United States had acquired vast amounts of land in the 1803 Louisiana Purchase, and since the 1840s Douglas had sought to establish a territorial government in a portion of the Louisiana Purchase that was still unorganized. Douglas's efforts were stymied by Senator David Rice Atchison of Missouri and other Southern leaders who refused to allow the creation of territories that banned slavery; slavery would have been banned because the Missouri Compromise outlawed slavery in the territory north of latitude 36°30' north (except for Missouri). To win the support of Southerners like Atchison, Pierce and Douglas agreed to back the repeal of the Missouri Compromise, with the status of slavery instead decided based on "popular sovereignty". Under popular sovereignty, the citizens of each territory, rather than Congress, would determine whether slavery would be allowed.

Douglas's bill to repeal the Missouri Compromise and organize Kansas Territory and Nebraska Territory won approval by a wide margin in the Senate, but faced stronger opposition in the House of Representatives. Though Northern Whigs strongly opposed the bill, it passed the House with the support of almost all Southerners and some Northern Democrats. After the passage of the act, pro- and anti-slavery elements flooded into Kansas to establish a population that would vote for or against slavery, resulting in a series of armed conflicts known as "Bleeding Kansas". Douglas and Pierce hoped that popular sovereignty would help bring an end to the national debate over slavery, but the Kansas–Nebraska Act outraged Northerners. The division between pro-slavery and anti-slavery forces caused by the Act was the death knell for the ailing Whig Party, which broke apart after the Act. Its Northern remnants would give rise to the anti-slavery Republican Party. The Act, and the tensions over slavery it inflamed, were key events leading to the American Civil War.