Wilmot Proviso

The Wilmot Proviso, one of the major events leading to the American Civil War, would have banned slavery in any territory to be acquired from Mexico in the Mexican War or in the future, including the area later known as the Mexican Cession, but which some proponents construed to also include the disputed lands in south Texas and New Mexico east of the Rio Grande.

Congressman David Wilmot first introduced the Proviso in the United States House of Representatives on August 8, 1846 as a rider on a $2,000,000 appropriations bill intended for the final negotiations to resolve the Mexican–American War. (In fact this was only three months into the two-year war.) It passed the House but failed in the Senate, where the South had greater representation. It was reintroduced in February 1847 and again passed the House and failed in the Senate. In 1848, an attempt to make it part of the Treaty of Guadalupe Hidalgo also failed. Sectional conflict over slavery in the Southwest continued up to the Compromise of 1850.