Answer:
The Missouri Compromise of 1820 contribute to the Southern secession is discussed below in details.
Step-by-step explanation:
Missouri Compromise of 1820
Maine and Missouri applied to join the Union. The Missouri compromise allowed both to become the part of the Union, Maine as a free state and Missouri as a Slave state.
Louisiana territory north of the southern boundary of Missouri would be free. Permitted slave masters to pursue fled slaves in the North.
Southerners were outraged that congress gave itself the authority to make laws about slavery. the North did not want slavery but the South did and when the congress allowed another state to be a slave state the north was angered.