The Missouri Compromise
In 1819, Missouri wanted to join the U.S. as a slave state. The U.S. already had twenty two states, half of which were slave states, and they didn't want to disrupt the balance. The Missouri compromise allowed Missouri to join the Union as a slave state, but also separated Maine from Massachusetts, making another free state. Without the compromise, it is unlikely that Missouri ever would have been able to join the United States.
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