Martin County is a county located in the U.S. state of North Carolina. As of the 2020 census, the population was 22,031. Its county seat is Williamston. The county was formed in 1774 from the southeastern part of Halifax County and the western part of Tyrrell County. It was named for Josiah Martin, the last royal governor of North Carolina. Whereas Do…Martin County is a county located in the U.S. state of North Carolina. As of the 2020 census, the population was 22,031. Its county seat is Williamston. The county was formed in 1774 from the southeastern part of Halifax County and the western part of Tyrrell County. It was named for Josiah Martin, the last royal governor of North Carolina. Whereas Dobbs County and Tryon County, named for Martin's predecessors Arthur Dobbs and William Tryon, were abolished after American independence, Martin County was neither abolished nor renamed.