Slavery & the Mexican War

Slavery, already a divisive issue for Americans, became even more of a flashpoint during the Mexican War. The Missouri Compromise of 1820 allowed for the entry of one slave state and one free state into the United States at the same time; any western territory south of the Missouri state line would become a slave state, while those above that line would remain free states. With Texas’ southern location, many northerners believed that President James K. Polk, a Democrat and slave owner from the South, went to war with Mexico to annex new territory and allow the growth of slavery into these areas. Northern Whigs, who argued against the war with Mexico, were convinced of this when Polk refused to fight Great Britain to obtain the Oregon territory—territory that would give the North a political advantage. The Whigs and Democrats continued their argument over the annexation of new Southern territory throughout the war and afterward.