There are 9 US Post Offices in Atascosa County serving a total of 45,949 residents equating to 5,105 residents per post office. It's estimated that approximately 73,340 packages are handled across the 9 county post offices annually. Atascosa County is a county located in the U.S. state of Texas. As of the 2010 census, the population was 44,911. Its county seat is Jourdanton. The county was formed in 1856 from Bexar County and is named for the Atascosa River. Atascosa County is part of the San Antonio-New Braunfels, TX Metropolitan Statistical Area."