There are 10 US Post Offices in Richland County serving a total of 78,081 residents equating to 7,808 residents per post office. It's estimated that approximately 124,626 packages are handled across the 10 county post offices annually. Richland County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 124,475. Its county seat is Mansfield. The county was created in 1808 and later organized in 1813. It is named for the fertile soil found there. Richland County is included in the Mansfield, OH Metropolitan Statistical Area as well as the Mansfield-Ashland-Bucyrus, OH Combined Statistical Area. The county is part of Northeast Ohio."