How did the Missouri Compromise balance the interests of pro-slavery and antislavery Americans?

The first major debate over slavery occurred when the Missouri Territory applied for statehood as a slave state in 1819. Some Americans opposed the prospect of pro-slavery forces gaining more votes in Congress, so they opposed Missouri statehood. Thomas Jefferson famously referred to the debate over Missouri as "a fire bell ringing in the night," a warning to Americans that disagreements over slavery could prove explosive to the future of the republic. Ultimately, Congress passed the Missouri Compromise. To balance the addition of a new slave state, the compromise created the new free state of Maine. Then, the southern boundary of Missouri, (36 degrees, 30 minutes North latitude) became the new boundary line between slavery and freedom. As Americans moved westward, this boundary line was to be extended: north of the line, slavery would be prohibited; south of it, slavery would be permitted. The Missouri Compromise did not end the debate over slavery, but did prevent it from tearing the new nation in two.