Tom Green County is a county located on the Edwards Plateau in the U.S. state of Texas. As of the 2020 census, its population was 120,003. Its county seat is San Angelo. It sits at an elevation variation of 1,717 feet to 2,480 feet. The principal river in the county is the Concho, which is formed by the convergence of the North, Middle, and South Concho rivers.