There are 13 US Post Offices in Harnett County serving a total of 121,402 residents equating to 9,339 residents per post office. It's estimated that approximately 193,771 packages are handled across the 13 county post offices annually. Harnett County is a county located in the U.S. state of North Carolina. As of the 2010 census, the population was 114,678. Its county seat is Lillington, and its largest city is Dunn. Harnett County comprises the Dunn, NC Micropolitan Statistical Area, which is a part of the greater Raleigh-Durham-Chapel Hill, NC Combined Statistical Area, which had a 2013 estimated population of 2,037,430."