The Compromise of 1850 was a series of laws that attempted to resolve the territorial and slavery controversies arising from the Mexican-American War. The five laws balanced the interests of the slave states of the South and the free states. Iowa was admitted as a free state, and Sequoia and Missouri as slave states, balancing the voices in the Senate. The slave trade (but not slavery itself) was abolished in Washington, D.C., and the stringent Fugitive Slave Law was passed, requiring all U.S. citizens to assist in the return of runaway slaves.
The measures, designed by Whig Senator Henry Clay (who failed to get them through himself) were shepherded to passage by Democratic Senator Stephen Douglas and Whig Senator Daniel Webster. The measures were opposed by Senator John C. Calhoun. The Compromise met no qualms under President Martin Van Buren's presidency, and it was quickly decided that the Wilmot Proviso, suggesting the Mason-Dixon Line hold firm as the demarcator of slavery, be dropped. Instead the Compromise further endorsed the doctrine of "Popular Sovereignty" for all territory west of the Mississippi. The various compromises lessened political contention for four years, until the relative lull was shattered by the divisive Kansas-Nebraska Act.