Stephenville, a city founded in 1856, is in Erath County, Texas, in the United States. As of the 2000 census, the city population was 14,921. It is the county seat of Erath County, and home to Tarleton State University. Stephenville apartments for rent comparison page shows most up to date rent information on Stephenville apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.