There are 5 US Post Offices in Marion County serving a total of 30,180 residents equating to 6,036 residents per post office. It's estimated that approximately 48,171 packages are handled across the 5 county post offices annually. Marion County is a county located in the northeastern portion of the U.S. state of Missouri. As of the 2010 census, the population was 28,781. Its county seat is Palmyra. Unique from most third class counties in the state Marion has two courthouses, the second located in Hannibal. The county was organized December 23, 1826 and named for General Francis Marion, the \"Swamp Fox,\" who was from South Carolina and served in the American Revolutionary War. The area was known as the \"Two Rivers Country\" before organization. Marion County is part of the Hannibal, MO Micropolitan Statistical Area, which is included in the Quincy-Hannibal, IL-MO Combined Statistical Area."