Dunn is the most populous city of Harnett County, North Carolina, United States. The population was 8,446 at the 2020 census. It is, along wit…Dunn is the most populous city of Harnett County, North Carolina, United States. The population was 8,446 at the 2020 census. It is, along with Harnett County, part of the Anderson Creek, NC Micropolitan Statistical Area, which is also included in the Raleigh-Durham-Cary, NC Combined Statistical Area.