There are 12 US Post Offices in Duplin County serving a total of 69,511 residents equating to 5,793 residents per post office. It's estimated that approximately 110,947 packages are handled across the 12 county post offices annually. Duplin /\u02c8du\u02d0pl\u026an/ County is a county located in the U.S. state of North Carolina. As of the 2010 census, the population was 58,505. Its county seat is Kenansville."