The Great Lakes Geologic Mapping Coalition (GLGMC), consisting of state geological surveys from all eight Great Lakes states, the Ontario Geological Survey, and the U.S. Geological Survey, was conceived out of a societal need for unbiased and scientifically defensible geologic information on the shallow subsurface, particularly the delineation, interpretation, and viability of groundwater resources. Only a small percentage (<10%) of the region had been mapped in the subsurface, and there was recognition that no single agency had the financial, intellectual, or physical resources to conduct such a massive geologic mapping effort at a detailed scale over a wide jurisdiction. The...