1972. Geological Survey (U.S.). This map layer portrays the 2000 state and county boundaries of the United States, Puerto Rico, and the U.S. Virgin Islands. The map layer was crea... U.S. Geological Survey.
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1998. Causey, J. Douglas. and Geological Survey (U.S.). This datalayer is a point coverage representing mine and mineral resource occurrence data worldwide (most thoroughly within the U.S.) and was publi... U.S. Geological Survey.
1973. Geological Survey (U.S.). Relief shown by contours and spot heights.; Compiled in 1970.; Includes population key.; Source data U.S Dept. of the interior - Geological Survey ... U.S. Geological Survey.