Wilmot Proviso — Slavery Question Ignites Congress

Pennsylvania Congressman David Wilmot attached an amendment to a war appropriations bill prohibiting slavery in any territory acquired from Mexico. The House passed it; the Senate blocked it. The proviso, though never enacted, set off a fierce national debate that prefigured the Civil War, dividing both parties along sectional lines. President Polk privately opposed the proviso as unnecessarily inflammatory but had no power to stop the debate it unleashed.