In 1820, amid growing sectional tensions over the issue of slavery, the U.S. Congress passed a law that admitted Missouri to the Union as a slave state and Maine as a free state, while banning slavery from the remaining Louisiana Purchase lands located north of the 36º 30’ parallel.
The Missouri Compromise, as it was known, would remain in force for just over 30 years before it was repealed by the Kansas-Nebraska Act of 1854. In 1857, the Supreme Court ruled the compromise unconstitutional in the Dred Scott case, setting the stage for the nation’s final path toward the Civil War.
Pro- and Anti-Slavery Factions in Congress
When the Missouri Territory first applied for statehood in 1818, it was clear that many in the territory wanted to allow slavery in the new state. Part of the more than 800,000 square miles bought from France in the Louisiana Purchase in 1803, it was known as the Louisiana Territory until 1812, when it was renamed to avoid confusion with the newly admitted state of Louisiana.
Missouri’s bid to become the first state west of the Mississippi River, and to allow slavery within its borders, set off a bitter debate in a Congress that was—like the nation itself—already divided into pro- and anti-slavery factions. In the North, where abolitionist sentiment was growing, many people opposed the extension of the institution of slavery into new territory, and worried that adding Missouri as a slave state would upset the balance that currently existed between slave and free states in the Union. Pro-slavery Southerners, meanwhile, argued that new states, like the original 13, should be given the freedom to choose whether to permit slavery or not.
