Tuscaloosa County, Alabama. Tuscaloosa County is a county in the U.S. state of Alabama. As of the 2010 census, its population was 194,656. Its county seat and largest city is Tuscaloosa, the former state capital from 1826 to 1845. The county is named in honor of Tuskaloosa, a paramount chief of the Mississippian culture, considered ancestors of the Choctaw in the region.