Kansas-Nebraska Act Reopens Slavery in the North

Senator Stephen Douglas's Kansas-Nebraska Act, signed May 30, 1854, repeals the Missouri Compromise's prohibition of slavery north of 36°30' and replaces it with "popular sovereignty." The act shocks the North, destroys the Whig Party, triggers the founding of the Republican Party, and launches Bleeding Kansas — a guerrilla war over whether Kansas would be slave or free.