There are 9 US Post Offices in Jefferson County serving a total of 55,070 residents equating to 6,119 residents per post office. It's estimated that approximately 87,898 packages are handled across the 9 county post offices annually. Jefferson County is the easternmost county of the U.S. state of West Virginia. As of the 2010 census the population was 53,498. Its county seat is Charles Town. The county was founded in 1801. Jefferson County is part of the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area.