Named for shape, resembling Greek letter /\, and for evident origin of its land -- sedimentation at fork of North and South Sulphur Rivers. The first (1820-30) political activity here was oversight by the Sulphur Forks Indian Commission (of the United States) of the Caddo, Delaware, Quapaw, and Seminole inhabitants. After Texas independence in 1836, the Delta came under jurisdictions of Red River, Lamar, and Hopkins counties. Families and wagon trains from Kentucky, Tennessee, and other states--and from other parts of Texas--settled here as early as the 1830s. The people of the Delta in 1868 petitioned for creation of the county; in 1870 the Legislature of Texas complied. The county seat, a new town to be in the geographic center, was named for Leroy Cooper, chairman of the House Committee on Counties and Boundaries. Gov. E.J. Davis named as commissioners to organize the county: Joel Blackwell, John P. Boyd, James Hamilton, J.W. Iglehart, and Thomas J. Lane. To supervise sales of lots in Cooper, Erastus Blackwell was appointed sheriff. The organizing election was held on Oct. 6, 1870, naming Charles S. Nidever as Chief Justice. Commissioners elected were John P. Boyd, J.F. Alexander, Alfred Allen and J.M. Bledsoe. (1970)