This data set describes ground-water regions in the United States defined by the U.S. Geological Survey. These ground-water regions are useful for dividing the United States into areas of roughly similar hydrologic characterstics and water-use patterns. Most of these regions are very generalized and were developed from a illustration published at a scale of approximately 1:20 million. The data set also includes polygon features for unconsolidated watercourses taken from 1:7,500,000-scale U.S. Geological Survey map of productive aquifers.