Wilmot Proviso

The Wilmot Proviso proposed an American law to ban slavery in any territory acquired from Mexico in the Mexican War. The conflict over the proviso was one of the major events leading to the American Civil War.

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 (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 political disputes over slavery in the Southwest continued until the Compromise of 1850.

After an earlier attempt to acquire Texas by treaty had failed to receive the necessary two-thirds approval of the Senate, the United States annexed the Republic of Texas by a joint resolution of Congress that required simply a majority vote in each house of Congress. President John Tyler signed the bill on March 1, 1845, a few days before his term ended. As many expected, the annexation led to war with Mexico. After the capture of New Mexico and California in the first phases of the war, the political focus shifted to how much territory would be acquired from Mexico. The key to this was the determination of the future status of slavery in any new territory.

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