The thorny subject of slavery's extension into newly acquired areas following the Louisiana Purchase was handled by the Missouri Compromise, which was approved in 1820.

To preserve the balance of power between slave and free states in Congress, it permitted Maine to become a free state and admitted Missouri as a slave state. The agreement also defined the 36°30′ parallel as the border for upcoming states, beyond which slavery was forbidden (except Missouri). This temporary fix for the issue of slavery in America was a reflection of the rising divisions among the various American sections.