A hydrogeologic framework of the Ozark Plateaus aquifer system was constructed as the base for a groundwater flow model developed as part of the U.S. Geological Survey Water Availability and Use Science Program to aid in the understanding of groundwater availability in select aquifer systems of the United States. The Ozark Plateaus aquifer system study area (hereinafter referred to as the “Ozark system”) is nearly 70,000 square miles and includes parts of Arkansas, Kansas, Missouri, and Oklahoma. A hydrogeologic framework was constructed to represent the altitudes and thicknesses of nine hydrogeologic units within the Ozark Plateaus aquifer system - . the Western Interior Plains confining system, Springfield Plateau aquifer, the Ozark confining unit, Ozark aquifer (divided into the upper, middle, and lower Ozark aquifers to better capture the spatial variation in the hydrologic properties), the St. Francois confining unit, the St. Francois aquifer, and the Basement confining unit. The formations that make up the hydrogeologic units of the Ozark system range from Pennsylvanian to Cambrian age. The scope of effort included the compilation and interpretation of hydrogeologic altitudes from geophysical, lithologic driller description, and well cutting logs. The final compiled dataset included more than 23,000 individual altitude points (excluding synthetic points) representing the nine hydrogeologic units. Shorthand names were used to identify points, extents, and raster surfaces corresponding to each hydrogeologic unit. WIPCS = Western Interior Plains confining system SPA = Springfield Plateau aquifer OCU = Ozark confining unit UOA = upper Ozark aquifer MOA = middle Ozark aquifer LOA = lower Ozark aquifer SFCU = St. Francois confining unit SFA = St. Francois aquifer BCU = basement confining unit