There are 6 US Post Offices in Custer County serving a total of 27,361 residents equating to 4,560 residents per post office. It's estimated that approximately 43,671 packages are handled across the 6 county post offices annually. Custer County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 27,469. Its county seat is Arapaho. The county was named in honor of General George Armstrong Custer. Custer County comprises the Weatherford, OK Micropolitan Statistical Area.