Presidential Election of 1848

The Wilmot Proviso & the Treaty of Guadalupe Hidalgo

David Wilmot (Pennsylvania) introduced legislation stating that slavery should be prohibited in all territory acquired as a result of the war with Mexico. Although this legislation never became law, it fostered a schism within the Democratic Party, most notably in New York. Lewis Cass (Michigan) offered a path to Democratic unity. In December 1847, Cass penned a letter to A.O.P. Nicholson of Tennessee, addressing the questions raised by the Wilmot Proviso. He stated that the people residing in each official U.S. territory should possess the authority to decide for themselves whether they wanted to legalize slavery in their domain. In articulating the rational for popular sovereignty, Cass mended Democratic fences and paved the way for his nomination at the 1848 national convention.

The United States treaty concluding the war with Mexico in February 1848 was called the Treaty of Gua-dalupe Hidalgo. The United States acquired California, New Mexico, what would become Nevada, Utah, and Arizona, and parts of Colorado and Wyoming. Furthermore, in 1846, the United States settled a dispute with Great Britain over the Oregon Territory. The countries used the 49th parallel as the dividing line: Below it, the United States carved out Washington, and above it, Britain received British Columbia.

The National Conventions

The Wilmot Proviso, the territorial agreement with Great Britain, and the Treaty of Guadalupe Hidalgo all created dissension among the national Democrats, northern Democrats harbored concerns that the northwest territorial acquisitions did not match the growth in the southwest. They wanted the two regions to keep pace balancing slave and free territories. Furthermore, growing anti-slavery sentiment in the north pushed the debate over the extension of slavery to the forefront.

The divisiveness of this issue crystallized in the schism of the New York State Democrats. Barnburners consisting of Martin Van Buren supporters who favored reforms and opposed the extension of slavery. Hunkers were conservatives with ties to traditional and southern Democrats. Cass's endorsement of popular sovereignty unified the majority of the national Democrats, but not the Barnburners. The Democrats convened in May in Baltimore and selected Cass as the party nominee on the 4th ballot. William O. Butler was nominated for the vice presidency. Cass not only hailed from Michigan, but boasted a great deal of support from Ohio. Butler represented the state of Kentucky on the national ticket.

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