There are 5 US Post Offices in Pecos County serving a total of 15,569 residents equating to 3,114 residents per post office. It's estimated that approximately 24,850 packages are handled across the 5 county post offices annually. Pecos County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 15,507. The county seat is Fort Stockton. The county was created in 1871 and organized in 1875. It is named for the Pecos River. It is one of the nine counties that comprise the Trans-Pecos region of West Texas."