The Free Soil Party was a short-lived political party in the United States that emerged in the late 1840s, primarily focused on opposing the expansion of slavery into the western territories. Formed by discontented members of the Democratic and Whig parties, it advocated for free soil for free men, emphasizing that slavery should not extend into new lands acquired during the Mexican-American War. The party played a crucial role in shaping the political landscape during a time of growing sectional tensions over slavery.