 The county seat is Dillon.Founded in 1910 from a portion of Marion County, both Dillon County and the city of Dillon were named for prosperous local citizen James W. Dillon (1826-1913), an Irishman who settled there and led a campaign to bring the railroad into the community.The result of this effort was the construction of the Wilson Short Cut Railroad, which later became part of the Atlantic Coast Line Railroad, and brought greater prosperity to the area by directly linking Dillon County to the national network of railroads.