There are 20 US Post Offices in Jefferson County serving a total of 70,192 residents equating to 3,510 residents per post office. It's estimated that approximately 112,034 packages are handled across the 20 county post offices annually. Jefferson County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 69,709. Its county seat is Steubenville. The county is named for Thomas Jefferson, who was at the time Vice President. Jefferson County is part of the Weirton-Steubenville, WV-OH Micropolitan Statistical Area, which is also included in the Pittsburgh-New Castle-Weirton, PA-WV-OH Combined Statistical Area."