Kansas–Nebraska Act

The 1854 U.S. law organized Kansas and Nebraska territories and let settlers decide whether slavery would be permitted, repealing the Missouri Compromise line.

Popular sovereignty: The principle that a territory’s residents should decide whether slavery would be legal there. The act used this principle to determine slavery’s status in Kansas and Nebraska.
Stephen A. Douglas: An Illinois senator and leading architect of the Kansas–Nebraska Act. Douglas introduced and championed the bill as a way to organize the territories.
David Atchison: A Missouri senator and prominent proslavery Democrat who supported extending slavery into Kansas Territory. His advocacy helped spur proslavery Missourians to influence Kansas politics.
Republican Party: A U.S. political party founded in the 1850s to oppose the expansion of slavery into western territories. Opposition to the act helped bring the new party together.
Missouri Compromise: The 1820 agreement that admitted Missouri as a slave state and barred slavery north of latitude 36°30′ in much of the Louisiana Purchase. The act nullified its restriction on slavery north of 36°30′.
Compromise of 1850: A package of U.S. laws that addressed disputes over slavery in territories acquired from Mexico and strengthened fugitive-slave enforcement. Its territorial popular-sovereignty approach helped set a precedent for the act.
Salmon P. Chase: An Ohio senator and antislavery politician who opposed the Kansas–Nebraska Act. Chase helped organize congressional opposition and public protest against the bill.
Whig Party: A major U.S. political party that opposed Andrew Jackson and collapsed in the 1850s amid sectional divisions. The act deepened the divisions that helped destroy the Whig Party.
Bleeding Kansas: The violent conflict between proslavery and antislavery forces in Kansas Territory during the 1850s. Competing settlers fought over the territorial vote the act authorized.
Transcontinental railroad: A rail line connecting the eastern and western United States, completed in 1869. Organizing Nebraska Territory was tied to political competition over a future central rail route.

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