There are 7 US Post Offices in Marshall County serving a total of 55,311 residents equating to 7,902 residents per post office. It's estimated that approximately 88,283 packages are handled across the 7 county post offices annually. Marshall County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 37,144. Its county seat is Holly Springs. The county is named for Chief Justice of the United States John Marshall. Marshall County is part of the Memphis, TN\u2013MS\u2013AR Metropolitan Statistical Area."