This data set consists of digital water-level elevation contours for the Tillman terrace and alluvial aquifer in southwestern Oklahoma. The Tillman terrace and alluvial aquifer is an unconfined aquifer that extends over an area of approximately 285 square miles and is used for irrigation and domestic purposes. The aquifer encompasses the unconsolidated terrace deposits and river alluvium associated with the North Fork of the Red River and the Red River in the western half of Tillman County. These sediments consist of discontinuous layers of clay, sandy clay, sand, and gravel. Water-level elevation contours for ground-water levels measured in 1969 were digitized from a paper map in a thesis in which the ground-water flow was modeled in the Tillman terrace and alluvial aquifer. The map was published at a scale of 1:249,695. Water-level elevations ranged from about 1,360 feet above sea level in the eastern part of the aquifer to 1,120 feet above sea level in the southern part of the aquifer.