There are 15 US Post Offices in Cumberland County serving a total of 287,425 residents equating to 19,162 residents per post office. It's estimated that approximately 458,762 packages are handled across the 15 county post offices annually. Cumberland County is a county located in the U.S. state of North Carolina. As of the 2010 census, the population was 319,431, making it the fifth-most populous county in North Carolina. Its county seat is Fayetteville. Cumberland County is part of the Fayetteville, NC Metropolitan Statistical Area."