Answer:
Northern representatives feared Missouri being admitted as a slave state because they didn't want the South to control Congress. To avoid this situation, the Missouri Compromise was signed in 1820.
The Missouri Compromise, also known as the Compromise of 1820, was a treaty between slave advocates and abolitionists in the United States.
The Missouri Compromise meant that in all states north of the 36 ° latitude, except Missouri and states east of Missouri, slavery would be prohibited. In states south of the latitude, it was permissible if authorities and (the free) population so desired. In connection with this, Maine was also broken out of Massachusetts and incorporated as a free state, which occurred March 15, 1820.
