There are 9 US Post Offices in Knox County serving a total of 61,280 residents equating to 6,809 residents per post office. It's estimated that approximately 97,810 packages are handled across the 9 county post offices annually. Knox County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 60,921. Its county seat is Mount Vernon. The county is named for Henry Knox, an officer in the American Revolutionary War who was later the first Secretary of War. Knox County comprises the Mount Vernon, OH Micropolitan Statistical Area, which is also included in the Columbus-Marion-Zanesville, OH Combined Statistical Area."