1) The spread of slavery became an issue when Missouri sought to enter the Union as a slave state, which would have given slave states more power than free states.
2) The Missouri Compromise admitted Missouri as a slave state and Maine as a free state, dividing the country along the 36°30' parallel with slavery allowed below and forbidden above.
3) The Kansas-Nebraska Act repealed the Missouri Compromise by organizing the territories of Kansas and Nebraska and allowing settlers there to determine through popular sovereignty if they would allow slavery, resulting in violent conflict between pro- and anti-slavery settlers in "Bleeding Kansas" from 1854-1856.
5. A compromise that admitted Missouri as a slave state and Maine as a free state. A line was drawn at 36 30’N. North would be free & South would be slave. 2
8. A plan by David Wilmot of Pennsylvania that called for the outlaw of slavery in any land won from Mexico. House passed bill but Senate defeated it. 3
41. A slave who lived in Missouri, later moved to Illinois and Wisconsin where slavery was illegal. When owner died, filed suit claiming he should be free. 14