The U.S. war fought primarily over the issue of slavery was the Civil War.

Fought from 1861 to 1865, the Civil War was a conflict between the Northern states (the Union) and the Southern states (the Confederacy) that seceded from the Union. While economic and political factors also played roles, the central issue was the expansion of slavery into new territories and states. The war resulted in significant loss of life and ultimately led to the abolition of slavery with the ratification of the 13th Amendment in 1865, reshaping the nation’s social and political landscape.