Quanah /ˈkwɑːnə/ is a city in and the county seat of Hardeman County, Texas, United States. As of the 2010 census the population was 2,641, down from 3,022 at the 2000 census.Quanah is 192 miles northwest of Fort Worth and 8 miles south of the Red River, which forms the Oklahoma-Texas state line. Copper Breaks State Park is 12 miles south of the city.