Popular sovereignty was the politic

Popular sovereignty was the political doctrine that the people who lived in a region should determine for themselves the nature of their government. In U.S. history, it was applied particularly to the idea that settlers of federal territorial lands should decide the terms under which they would join the Union, primarily applied to the status as free or slave. The first proponent of the concept was Senator Lewis Cass of Michigan, who put the idea forward while opposing the Wilmot Proviso in 1846.