This aquifer atlas describing the Winona-Tallahatta aquifer is the seventh in a series prepared in cooperation with the Mississippi Board of Water Commissioners. The atlas summarizes the large amount of unpublished data available in the files of the U.S. Geological Survey and it describes the extent, character, and present utilization of the aquifer and its potential for additional development. The Winona-Tallahatta aquifer, which contains freshwater having less than 1,000 mg/liter of dissolved solids in about 25 percent of the State occurs in northwestern and central Mississippi. The water-bearing zones extend into Tennessee and become part of the Memphis aquifer. In Arkansas and Louisiana the aquifer is in the Cane River Formation. The Tallahatta Formation which is the basal unit of the Claiborne Group includes, in ascending order, the Meridian Sand, Basic City Shale, and Neshoba Sand Members. The Winona-Tallahatta aquifer is the source of water for only a few large water users, but is the source of water for hundreds of small-yield domestic and stock wells less than 200 feet deep. Total water use in the State in 1977 from the Winona-Tallahatta is estimated to be about 3 mdg. (Woodard-USGS)