There are 6 US Post Offices in Stephens County serving a total of 44,953 residents equating to 7,492 residents per post office. It's estimated that approximately 71,750 packages are handled across the 6 county post offices annually. Stephens County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 45,048. Its county seat is Duncan. The county was created at statehood, partly from the Chickasaw Nation in Indian Territory and partly from Comanche County in Oklahoma Territory. It was named for Texas politician John Hall Stephens. Stephens County comprises the Duncan, OK Micropolitan Statistical Area.