There are 7 US Post Offices in Highland County serving a total of 42,535 residents equating to 6,076 residents per post office. It's estimated that approximately 67,891 packages are handled across the 7 county post offices annually. Highland County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 43,589. Its county seat is Hillsboro. The county is named for the topography which is hilly and divides the watersheds of the Little Miami and Scioto Rivers."