March 6, 1820: The Missouri Compromise is ratified.

The issue of slavery was, in the early years of the United States, treated cautiously, handled warily, and often tip-toed around altogether. In the Constitution, slaves were only vaguely referred to - as “such Persons” and  ”other Persons”. Article one, section nine of the U.S. Constitution provided the earliest year Congress would be able to abolish the slave trade (1808) but was mum on the subject of slaves already living in the country and the countless thousands who would be born into bondage in the future. Therefore, responsibility for dealing with the future of slavery and the debate between slaveowners and northerners over the westward spread of slavery was shifted to the federal government, which fumbled with the subject as well for decades until its resolution by the Thirteenth Amendment. 

The acquisition of the Louisiana Territory in 1803 exacerbated the conflict. When Missouri requested admission to the Union as a slave state in 1819, the government was faced with an important decision regarding sectional balance, settled finally by the Missouri Compromise; this solution temporarily quieted debate until its terms were violated by the provisions of the Kansas-Nebraska Act of 1854, but until then, it remained an inviolable and almost sacred resolution. The Missouri Compromise prohibited slavery in the Louisiana Territory north of the 36° 30´ latitude line except for Missouri, which was admitted as a slave state. At the same time, the state of Maine was also created and admitted to the Union, thereby maintaining a balance between slave and free states. In 1854, the Kansas-Nebraska Act opened the territories of Kansas and Nebraska to popular sovereignty, through which residents rather than the federal government could decide the future of slavery in their respective territories despite the fact that the Missouri Compromise had closed Kansas to slavery. 

In 1857, the Taney Court ruled (on same day as the ratification of the 1820 Compromise) in Dred Scott v. Sandford  African-Americans were not permitted to sue in federal court, and also that the Missouri Compromise had never been constitutional in the first place, because slaves, like farm animals, were “property” that the federal government could not take away under the Fifth Amendment.