There are 15 US Post Offices in Marion County serving a total of 97,727 residents equating to 6,515 residents per post office. It's estimated that approximately 155,983 packages are handled across the 15 county post offices annually. Marion County is a county located in the U.S. state of West Virginia. As of the 2010 census, the population was 56,418. Its county seat is Fairmont. The county was named in honor of General Francis Marion (ca. 1732\u20131795), known to history as \"The Swamp Fox\". Marion County comprises the Fairmont, WV Micropolitan Statistical Area, which is also included in the Morgantown-Fairmont, WV Combined Statistical Area.