Atascosa County was formed in 1856 south of Bexar County. While growth began around 1840 when veterans of the Texas Revolutionary War were granted land, the grant that marked the extensive colonization was that of four leagues on the Atascosa River to José Antonio Navarro, awarded by the Mexican government in 1825 and recognized by the State of Texas in 1853.
As of the 2014 census, the population was 44,744. Jourdanton, Atascosa County's seat of Government, is located off highways 16 and 97, about 33 miles south of San Antonio.
Atascosa County is part of the San Antonio - New Braunfels Metropolitan Statistical Area.