There are 3 US Post Offices in Murray County serving a total of 13,031 residents equating to 4,344 residents per post office. It's estimated that approximately 20,799 packages are handled across the 3 county post offices annually. Murray County is a county located in the southern part of the U.S. state of Oklahoma. As of the 2010 census, the population was 13,488. This is a 6.9 percent increase from 12,623 at the 2000 census. The county seat is Sulphur. The county was named for William H. Murray, a member and president of the Oklahoma Constitutional Convention and later a Governor of Oklahoma.