United States. Geological Survey. U.S.G.S. Alternate title: Burlington, PA. Polyconic projection. Relief shown by 20 feet contour interval and spot heights. Surveyed in 1885-88, and accepted in cooperation. Revised in 1904 under direction of H. M. Wilson, geographer, by J. M. Whitman. Triangulation by U.S. Coast and Geodetic and New Jersey Geological Surveys. Verso: The topographic maps of the United States.