There are 2 US Post Offices in Harrison County serving a total of 18,672 residents equating to 9,336 residents per post office. It's estimated that approximately 29,803 packages are handled across the 2 county post offices annually. Harrison County is a county located in the U.S. state of Kentucky. As of the 2010 census, the population was 18,846. Its county seat is Cynthiana. The county was founded in 1793 and named for Colonel Benjamin Harrison, an advocate for Kentucky statehood, framer of the Kentucky Constitution, and Kentucky legislator."