Capture of O’Brien’s Guns at Buena Vista, by Samuel E. Chamberlain, ca. 1850s
The Mexican War added more than 500,000 square miles to the nation and raised the question in Congress of whether slavery should be allowed in the new territory.
The San Jacinto Museum of History, Houston
Taking a Stand, 1848
Adding controversial amendments to important bills is one tactic used by supporters of a bill to make other lawmakers confront and vote on difficult issues. Representative David Wilmot of Pennsylvania used this technique in a classic example of parliamentary acrobatics. In 1846, Wilmot successfully added to an appropriations bill (one that authorizes necessary government expenditures) an amendment prohibiting slavery in all territory taken during the Mexican War. The Senate, where the South was stronger, let the bill die. The antislavery House majority continued adding Wilmot’s proviso to other important bills, constantly forcing legislators to face the volatile question of expanding slavery.