Missouri applied for statehood on December 18, 1818. Shortly after, John Tallmadge of New York presented an amendment that would require that Missouri abolish slavery as a condition for admission as a state. From here the debate began. The South felt that the U.S. government had no power to restrict slavery, which was protected under the Constitution. The North felt that slavery was evil and should be restricted to the current slave states. In 1819, Maine put in its application for statehood. Then a compromise developed.
By 1820, this compromise had been realized as two bills were passed. The first made Maine the 23rd state. The second admitted Missouri as a slave state and set the parallel 36°30' as the dividing line between enslaved and free states as the country continued to expand. This compromise was successful. Although some people continued to argue over slavery, most people began to view the compromise as sacred.
In 1854 the Missouri Compromise was repealed as part of the Kansas-Nebraska Act. At the time, debates were occurring over where the transcontinental railroad would run. Illinois senator Stephen Douglas desired it to run through Chicago, and he needed Southern support. This would be no easy task. He achieved this by making a deal. He turned the Nebraska Territory into two states (Nebraska and Kansas). These states, despite being north of the 36°30' parallel, would be either slave or free based on the principle of popular sovereignty. With the passage of this bill the Missouri Compromise was effectively undone. Three years later, in 1857, Chief Justice Roger Taney ruled in the case Dred Scott v. Sanford, more famously known as the Dred Scott decision, that the Missouri Compromise was unconstitutional, officially opening up all new states to slavery.
The repeal of the Missouri Compromise was more impactful, according to historian Robert Forbes, than the compromise itself. While it effectively settled the question of slavery from 1820 to 1854, its repeal began the sectarian conflict that eventually brought the nation into the Civil War.
Popular sovereignty - a doctrine, held chiefly by slave owners, that the people living in a territory should be free of federal interference in determining domestic policy, especially with respect to slavery
Sectional - pertaining or limited to a particular section; local or regional.