What was the last effort proposed to prevent secession by returning to the Missouri Compromise?

The Crittenden Compromise was an attempt made at the end of 1860 to avert the secession of Southern states from the Union. Proposed by Senator John J. Crittenden, the plan sought to extend the Missouri Compromise line westward to the Pacific Ocean, thereby allowing slavery in territories south of the line while prohibiting it in those to the north. This compromise aimed to assuage the concerns of Southern states by essentially reinstating the territorial divisions that had been established earlier and providing a framework that many believed could maintain the Union.

The Crittenden Compromise was significant because it represented a last-ditch effort to resolve the disputes between pro-slavery and anti-slavery factions through compromise, reflecting the heightened tensions leading up to the Civil War. However, it ultimately failed to gain sufficient support from Congress, illustrating the deep divisions within the country at that time. The other choices, like the Lecompton Constitution and the Kansas-Nebraska Act, were involved in the contentious debates surrounding slavery in the territories but did not propose a solution aimed explicitly at returning to the Missouri Compromise framework. The Freeport Doctrine was more about the rights of territories to decide the issue of slavery themselves rather than a compromise solution to prevent secession