There are 7 US Post Offices in Pawnee County serving a total of 16,798 residents equating to 2,400 residents per post office. It's estimated that approximately 26,811 packages are handled across the 7 county post offices annually. Pawnee County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 16,577. Its county seat is Pawnee. The county is named after the Pawnee Tribe. Pawnee County is included in the Tulsa, OK Metropolitan Statistical Area.