In and before 1820, tensions were high in the North and the South because of slave states vs. free states. The free states were afraid that the slave states would have too much power in the Senate. Therefore, the Missouri Compromise was born. Missouri became a slave state, and Maine joined as a free state. They chose which parts of the Louisiana Purchase would become slave territory and which parts would not. Because of the Missouri Compromise, tensions between the North and South states were reduced. It was the key factor in delaying the Civil War.