United States. Geological Survey. U.S.G.S. Alternate title: Delaware Watergap, PA.-N.J. Polyconic projection. Relief shown by 20 feet contour interval and spot heights. Surveyed in 1895-1888 and 1936. Verso: Delaware Water Gap.
Publisher:
[Washington, D.C.] : U.S. Geological Survey, 1936.