This data set consists of digital aquifer boundaries for the alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in central Oklahoma. Ground water in approximately 400 square miles of Quaternary-age alluvial and terrace aquifer is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer consists of clay, silt, sand, and gravel. Sand-sized sediments dominate the poorly sorted, fine to coarse, unconsolidated quartz grains in the aquifer. The hydraulically connected alluvial and terrace deposits unconformably overlie Permian-age formations. The aquifer is overlain by a layer of wind-blown sand in parts of the area. The aquifer boundaries established in a ground-water modeling report and are available in this data set include areas: 1) where the alluvial and terrace deposits have been deposited against relatively impermeable Permian-age formations; 2) where the underlying Permian-age formations crop out within the alluvial and the terrace deposits due to protruding high spots on the Permian-age formations irregular surface; 3) where the aquifer extends beyond the geographic limit of the study area defined in the ground-water modeling report; and 4) where the aquifer has little or no saturated thickness. The lines in the data set representing aquifer boundaries along geological contacts were extracted from published digital surficial geology data sets based on a scale of 1:250,000. Boundaries defining the northwest and southeast geographic limits of the aquifer and areas of little or no saturated thickness were digitized from folded paper maps, at a scale of 1:250,000, in the ground-water modeling report.