There are 2 US Post Offices in Mcmullen County serving a total of 656 residents equating to 328 residents per post office. It's estimated that approximately 1,047 packages are handled across the 2 county post offices annually. McMullen County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 707, making it the fifth-least populous county in Texas. Its county seat is Tilden. The county was established from parts of Bexar County, Atascosa County, and Live Oak County in 1858 and later organized in 1877. It is named for John McMullen, founder of a colony in Texas. The McMullen County Courthouse was designed by the architect William Charles Stephenson, originally from Buffalo, New York. Stephenson also designed some fifty buildings in Beeville, including the Bee County Courthouse."