Kansas-Nebraska Act: Popular Sovereignty Repeals Missouri Compromise

Senator Stephen Douglas's Kansas-Nebraska Act repealed the Missouri Compromise of 1820 and replaced it with 'popular sovereignty' — settlers in each territory would vote on slavery. This opened Kansas and Nebraska territories, previously designated free, to potential slavery. The law shattered the Whig Party, created the Republican Party, and triggered a guerrilla war in Kansas. Pro-slavery forces from Missouri ('Border Ruffians') flooded Kansas to stuff ballot boxes, establishing a fraudulent pro-slavery territorial government. Anti-slavery settlers established a rival government. The result was years of violent conflict.