There are 10 US Post Offices in Grady County serving a total of 43,409 residents equating to 4,341 residents per post office. It's estimated that approximately 69,286 packages are handled across the 10 county post offices annually. Grady County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 52,431. Its county seat is Chickasha. It was named for Henry W. Grady, an editor of the Atlanta Constitution and southern orator. Grady County is part of the Oklahoma City, OK Metropolitan Statistical Area.