As the United States expanded following the Louisiana Purchase in 1803, the issue of slavery became a growing point of contention. In the North, states began banning slavery in state constitutions. In the South, slaves were in increasingly high demand. As more anti-slavery sentiment grew in the free states of the North, pro-slavery sentiment grew in the slave states of the South. As more people began to move to the land acquired through the Louisiana Purchase, the issue arose of admitting those territories as states.
With Missouri growing in population and applying for statehood, the big question was whether or not slavery would be permitted. To complicate issues, there was a balance of power in the US Senate between free and slave states. While free state senators hoped to eventually place a national ban on slavery, slave state senators hoped to protect the institution of slavery through federal legislation—or at the very least prevent its being banned.
Aside from maintaining a balance of power in Congress between free states and slave states, the Missouri Compromise aimed to resolve similar issues in the future regarding the rest of the land acquired in the Louisiana Purchase. This was established at the 36-30 latitude line. Slavery would be banned in areas of the Louisiana Purchase north of this line, while it would be permitted in areas of the Louisiana Purchase south of this line.
After much debate and a series of close votes in the House and the Senate, the Missouri Compromise was developed. The Missouri Compromise allowed for the admission of Missouri as a slave state, while simultaneously admitting Maine as a free state (the admission of both at the same time through the same piece of legislation also caused some consideration and debate). The admission of one free state and one slave state ensured that the balance in the U.S. Senate would be preserved. The Missouri Compromise also established the 36-30 latitude line as the border between territory where slavery would be permitted and territory where slavery would be banned.
On March 6, 1820, President Madison signed the Missouri Compromise into law. The Missouri Compromise would remain in effect until the passage of the Kansas-Nebraska Act in 1854. The Missouri Compromise was an attempt by the United States government to deal with the growing issue of slavery. It would delay the outbreak of conflict between pro-slavery and anti-slavery factions, but ultimately would fail to entirely prevent it.