Mexican American War

Under the terms of the treaty that ended the Mexican American War, the U.S. acquired over a half million square miles of new territory: all or parts of present-day Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. Immediately the question arose: would slave-owning settlers be allowed to bring their slaves with them, or would the new territory be reserved for free labor only?

The Northwest Ordinance of 1787 (authored by Thomas Jefferson) prohibited the introduction of slavery into the territory north of the Ohio River. In 1820, the Missouri Compromise (brokered principally by Henry Clay) allowed the admission of Missouri into the union as a slave state, but on the condition that other than in Missouri slavery would not be permitted north of the 36°30′ parallel (Missouri’s southern border). The acquisition of the new territory raised the sectional question again, with some demanding that slavery be permitted in all the new territory, some demanding that it be prohibited in all the new territory, some demanding that the 36°30′ parallel compromise line be extended to the Pacific (which would have the effect of making some of the territory open to slavery and some not), and some demanding that the question of slavery be left to the citizens of the territories. It was a difficult knot to untangle and the preservation of the Union was at stake.

After much debate, controversy and conflict, the matter was eventually resolved by the Compromise of 1850. Under the provisions of the Compromise, slavery was prohibited in California and Oregon (as opposed to extending the 36°30′ parallel to the ocean, which would have made slavery legal in southern California, but not northern California), in the Utah and New Mexico territories the question of slavery was to be determined by the will of the settlers, the slave trade (but not slaveholding itself) was prohibited in Washington D.C., and the fugitive slave provision of the Constitution was codified into law.

The Compromise of 1850 was the last hurrah for the men remembered by history as “The Great Triumvirate”: Senators Henry Clay, Daniel Webster, and John C. Calhoun. His health failing, Clay introduced the resolutions that made up the Compromise, then took a leave of absence from the Senate. While freshman Senator Stephen Douglas led the floor fight for passage, Clay did much of the hard work from his home in Kentucky. Webster’s reluctant support of the Compromise destroyed his reputation in New England and tarnished his career. From his deathbed, Calhoun railed against the Compromise, preferring immediate disunion.

After months of debate and angst, the resolutions were passed, delaying the crisis of disunion. Although none of the antagonists knew it at the time, the postponement of the crisis probably sealed the fate of its ultimate resolution. Had the southern states seceded in 1850, rather than 1861, the North likely would not have had the strength to stop them. But over the next decade the population and industrial might of the North would boom, so that by the time the war came the North had a decisive material advantage.

Henry Clay introduced the Resolutions that would become the Compromise of 1850.