Tuscaloosa County is a county of the U.S. state of Alabama.It is named in honor of the pre-Choctaw chief Tuskaloosa. In 2009, the population was estimated at 184,035. In 2000, the population was 164,875.The county is the second-largest in the state in terms of area (trailing only Baldwin County) and sixth-largest in terms of population (behind Jefferson, Mobile, Madison, Montgomery,and Shelby counties).Its seat and largest city is Tuscaloosa, the former state capital from 1826 to 1845. It is also the largest county in the Tuscaloosa, Alabama, Metropolitan Statistical Area.