What was the Wilmot Proviso and why did it increase sectional conflict?

The Wilmot Proviso was a significant congressional proposal introduced on August 8, 1846, by Pennsylvania Representative David Wilmot. It sought to prohibit the expansion of slavery into any territory acquired from Mexico following the Mexican-American War.12

The proposal intensified sectional conflict because it reopened the volatile issue of slavery's expansion, which had remained largely dormant since the Missouri Compromise. Northern abolitionists viewed the war as a calculated effort by Southern slave states to increase their political power by creating new slave-holding territories.2

Although the Proviso never passed both houses of Congress, it sparked bitter national debate and deepened the divide between the North and South. This ongoing struggle to address the status of slavery in new territories eventually contributed to the formation of the Republican Party in 1854, which adopted the principle of the Proviso as a core platform.12