Decatur (dɪˈkeɪtə(r)) is the largest city and county seat of Morgan County (with a portion also in Limestone County) in the U.S. state of Alabama. Nicknamed "The River City", it is located in northern Alabama on the banks of Wheeler Lake, along the Tennessee River. The population in 2020 was 57,938. Decatur is the core city of the two-county large Decatur metropolitan area, which had an estimated population of 156,494 in 2020. Combined with the Huntsville Metropolitan Area, the two create the Huntsville-Decatur Combined Statistical Area, of which Decatur is the second-largest city.