The Missouri Compromise was primarily a response to the growing tensions surrounding the expansion of slavery into new territories in America. As the United States continued to expand westward, questions arose regarding the status of slavery in these new regions. In 1819, when Missouri application to join the Union as a slave state was submitted, a fierce debate ignited within Congress. The House of Representatives, recognizing the need for a compromise, particularly after heated debates about the future of slavery in the prospective states of the Louisiana Purchase, put forth a solution. The Missouri Compromise allowed Missouri to enter as a slave state while simultaneously admitting Maine as a free state to maintain the balance between slave and free states in the Senate.

In addition to the admission of Missouri and Maine, the compromise also established a significant boundary line at 36°30′ north latitude. This boundary designated that all new territories and states north of this line would be free states, while those south of it could permit slavery. The passage of the compromise drew both supporters who viewed it as a fair resolution and critics who feared it would only serve to temporarily placate the underlying tensions that the slavery issue raised. For many, the compromise represented a critical moment of bipartisanship aimed at sustaining the fragile political balance between the North and South.

The Missouri Compromise passed through Congress with an understanding that it would help quell sectional conflict; however, it only served to highlight the deepening divide over slavery. The act not only had immediate implications for Missouri and Maine but also set a precedent for how future states would be admitted into the Union and how the issue of slavery would continue to evolve. The passage marked a crucial point in the sectional conflict that would ultimately culminate in the American Civil War nearly four decades later.