- Goldthwaite is the county seat of Mills County, Texas, and is centrally located at the crossroads of US Hwy 84, US Hwy 183, State Hwy 16, FM 574, and FM 2005. We are also served by Burlington/Santa Fe Railways. Our town has an estimated population of 2, 000. Goldthwaite got its beginning when the railroad began working its way to connect the East and West. The town was named after a man named ...centex.net/~city