David Wilmot in Causes of the Civil War
David Wilmot (1814-1868) was an American politician who sponsored a bill that promised to prohibit slavery in territory gained from Mexico in the Mexican-American War. Wilmot, a Democrat until the 1850s, opposed the expansion of slavery into the West but did not advocate abolition.
Certain of success in the war against Mexico, American political leaders debated the question of slavery's expansion. In late 1846, Pennsylvania Congressman David Wilmot suggested that slavery be banned in all new territory acquired from Mexico. His proposal, known as the "Wilmot Proviso," failed to pass, but the controversy it incited helped dismantle traditional political party alliances, as nearly all northerners supported the bill while most southerners opposed it.