There are 2 US Post Offices in Irion County serving a total of 1,504 residents equating to 752 residents per post office. It's estimated that approximately 2,401 packages are handled across the 2 county post offices annually. Irion County is a county located on the Edwards Plateau in the U.S. state of Texas. As of the 2010 census, its population was 1,599. Its county seat is Mertzon. The county is named for Robert Anderson Irion, a secretary of state of the Republic of Texas. Irion County is included in the San Angelo, TX Metropolitan Statistical Area.