The compromise was proposed by Henry Clay, who was the Speaker of the House of Representatives at the time. Clay was a slaveholder from Kentucky, and he was concerned that the addition of new slave states to the Union would lead to a civil war.
The compromise was based on the idea of maintaining a balance between slave and free states. Missouri would be admitted to the Union as a slave state, and Maine would be admitted as a free state. The remaining territory of the Louisiana Purchase would be divided into two parts, with the northern part being free territory and the southern part being slave territory.
The Missouri Compromise was a controversial measure, and it did not resolve the issue of slavery in the United States. The compromise was eventually overturned by the Dred Scott decision of 1857, which ruled that slaves were not citizens of the United States and could not sue in federal court. The Dred Scott decision led to the outbreak of the Civil War in 1861.