Antebellum Period: The Missouri Compromise of 1820

          Slave and free states maintained balanced power in the Senate in order to prevent congressional favor for the opposing side. This equilibrium was threatened when the Missouri territory declared they wanted to become a slave state. Massachusetts split in to two states, admitting Maine as a free state. Western territories were declaring statehood relatively frequently, so to prevent future tensions, Henry Clay compromised and drew a line across the 36 30 parallel thus, dividing America in half. Any new state above the line was to be admitted as free,and any new state South of the line as slave.

Above: Map of  the Missouri Compromise
Source:julieoverby.pbworks.com