Free-Soilers were members of a political movement in the mid-19th century that opposed the expansion of slavery into the territories of the United States. This group emerged during a time of intense national debate over slavery, advocating for the idea that free men on free soil constituted a morally and economically superior system to slavery. They played a crucial role in shaping the political landscape leading up to the Civil War, particularly as compromises around the issue of slavery began to fail.