The Wilmot Proviso was an addendum added to a $2,000,000 request for funds introduced to Congress by President James K. Polk following the Mexican War. Polk requested the funds to negotiate a peace treaty with Mexico. The proviso was attached to appease Northern abolitionists and to prevent the introduction of slavery into any new territory acquired as a result of the war.

The highly political bill caused a major stir in Congress and was never passed in the Senate or House of Representatives, despite the efforts of Northern politicians to re-introduce the bill several times during Congressional sessions. Political wrangling concerning the introduction of the bill resulted in strained relations between politicians in the North and South. The disagreements between Democrats and Whigs over the Wilmot Privoso and the larger issue of slavery resulted in the formation of the Republican Party in Ripon, Wisconsin in 1854.