The Kansas-Nebraska Act, which was passed in 1854, continued the ideas of the Missouri Compromise.
The Missouri Compromise aimed to maintain a balance between slave and free states by regulating the expansion of slavery into new territories. However, the Kansas-Nebraska Act effectively repealed the Missouri Compromise by allowing the territories of Kansas and Nebraska to decide for themselves whether to allow slavery through the principle of popular sovereignty. This led to significant conflict and violence in those territories, known as "Bleeding Kansas," as pro-slavery and anti-slavery factions clashed.