The Compromise of 1850 was passed by the U.S. Congress to settle slavery issues and to avert the dissolution of the Union. It stemmed from the request for statehood by the territory of California in 1849, which included a constitution banning slavery. California's admission to the Union would tip the balance in favor of free states—sixteen free states to fifteen slave states. A balance had been achieved with the Missouri Compromise of 1820, which tried to settle the growing slavery issue at that time by admitting Missouri as a slave state and Maine as a free state. The proposed admission of California in 1850 was further complicated by unresolved slavery questions in the vast southwestern territory that had been ceded to the United States after the war with Mexico ended in 1848 with the Treaty of Guadalupe Hidalgo.

As he had done with the Missouri Compromise thirty years earlier...