Missouri Compromise
Definition
A law passed by Congress in 1820 that admitted Missouri as a slave state and Maine as a free state, thus maintaining balance of power among slave and free states in the U.S. Senate, as well as prohibiting slavery north of the 30° 36' line of latitude. The Missouri Compromise was repealed by the Kansas-Nebraska Act in 1854 and declared unconstitutional in 1857 by the Supreme Court in Dred Scott v. Sandford.