Missouri Compromise

The Missouri Compromise of 1820 was a congressional agreement that regulated the extension of SLAVERY in the United States for thirty years. Under the agreement, the territory of Missouri was admitted as a slave state, the territory of Maine was admitted as a free state, and the boundaries of slavery were limited to the same latitude as the southern boundary of Missouri, 36°30′ north latitude.

By 1818 the rapid growth in population in the North had left the Southern states, for the first time, with less than 45 percent of the seats in the U.S. House of Representatives. The U.S. Senate was evenly balanced between eleven slave and eleven free states. Therefore, Missouri's 1818 application for statehood, if approved, would give the slave states a majority in the Senate and reduce the Northern majority in the House.

In 1819 the free territory of Maine applied for statehood. Speaker of the House HENRY CLAY of Kentucky saw this event as an opportunity to maintain the balance of free and slave states. He made it clear to Northern representatives that Maine would not be admitted without an agreement to admit Missouri. Clay persuaded opponents of slavery to drop efforts to ban it in the territories. In return, the Southern states agreed to limit slavery to the territory below 36°30′ north latitude. Under this provision the unsettled portions of the LOUISIANA PURCHASE north and west of Missouri would be free from slavery. The only area remaining for further expansion of slavery would be the territory that would become Arkansas and Oklahoma. To preserve the sectional equality in the Senate, Missouri and Maine were to be admitted to the Union simultaneously. Clay managed to pass the compromise in the House by a three-vote margin.

In 1821 Missouri complicated matters, however, by inserting a provision into its state constitution that prohibited free blacks and mulattoes from entering the state. Northern representatives objected to this language and refused to give final approval for statehood until it was removed. Clay then negotiated a second compromise that removed the offensive language from the Missouri constitution and substituted a provision that prohibited Missouri from discriminating against citizens from other states. Left unsettled was the question of who was a citizen. With this change Missouri and Maine were admitted to the Union.