Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands
This map layer contains the shallowest principal aquifers of the conterminous United States, 
Hawaii, Puerto Rico, and the U.S. Virgin Islands, portrayed as polygons.  The map layer 
was developed as part of the effort to produce the maps published at 1:2,500,000 in the 
printed series "Ground Water Atlas of the …