The United States Principal Aquifers (GIM-130): Miller, J. A. (compiler) (1:5,000,000; 1988), size 41" x 30". Description: Part of the National Atlas of the United States of America, this large-scale map of the principal aquifers of the United States delineates sixty-one aquifers in six categories: unconsolidated sand and gravel; semiconsolidated sand; sandstone; sandstone and carbonate rock; carbonate rock; and basaltic and volcanic-rock aquifers. Glacial deposit aquifers that overlie bedrock aquifers locally are also shown. Insets of Hawaii, Alaska, and Puerto Rico/Virgin Islands are included (USGS no. 101514).