Delta County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 5,230. Its county seat and largest city is Cooper. The county was founded in 1870 and is named for its triangular shape, which resembles the Greek letter delta.

Cooper is a city in and the county seat of Delta County, in the U.S. state of Texas. Located between the north and south forks of the Sulphur River, Cooper is the largest settlement in Delta County. At the 2020 United States census, the city had a population of 1,911.