In 1819, as Missouri began drafting a state constitution in preparation for statehood, New York congressman James Tallmadge introduced two antislavery amendments to the bill which allowed for the creation of Missouri as a state. Despite the fact that Tallmadge’s bills were not passed, the issue involving slavery threatened to explode.

The issue of slavery had remained controversial in America since 1787. In 1819, half of America’s twenty-two states were free states (northern), and half were slave states (southern). Because the free states had larger populations, they controlled the House of Representatives. Free and slave states shared equal representation in the Senate. The admission of Missouri as a free state or slave state would upset the balance. Antislavery members of Congress argued that slavery should be prohibited in new states, while pro-slavery members of Congress argued that the state should have the right to determine if slavery was legal or illegal within its borders.

A compromise was made when Maine applied for statehood in 1820. According to the deal thought of by Henry Clay, if the southern states agreed to the admission of Maine as a free state, Missouri would be admitted as a slave state. In addition, all lands acquired in the Louisiana Purchase north of 36° 30′ N latitude would be free. Both the free and the slave states agreed to Clay’s compromise, which lasted 30 years before being repealed following another period of American expansion.