The Missouri Compromise was a federal legislation passed in 1820 to maintain the balance of power in Congress between slave and free states. The key points of the compromise were:

• Admitting Missouri as a slave state and Maine as a free state at the same time, so as not to upset the balance between slave and free states in the nation.
• Prohibiting slavery in the Louisiana Territory north of the 36° 30´ latitude line, with the exception of Missouri.
• Offering the following propositions to the convention of the Missouri territory for their free acceptance or rejection: "That the further introduction of slavery or involuntary servitude be prohibited, except for the punishment of crimes, whereof the party shall have been duly convicted".

The Missouri Compromise was very controversial, and many worried that the country had become lawfully divided along sectarian lines. The compromise delayed the Civil War and sowed its seeds. In 1854, the Missouri Compromise was repealed by the Kansas-Nebraska Act, and three years later, it was declared unconstitutional by the Supreme Court in the Dred Scott decision.