"Polyconic projection. 1927 North American datum." "Contour intervals 25 and 40 feet with supplementary contours at 5 and 20 foot intervals." In margin: Contour interval diagram. Electronic reproduction. Cambridge, Mass. : Harvard Geospatial Library, 2008 Georeferenced image for use in a GIS.
"Polyconic projection. 1927 North American datum." "Contour intervals 25 and 40 feet with supplementary contours at 5 and 20 foot intervals." In margin: Contour interval diagram. Electronic reproduction. Cambridge, Mass. : Harvard Geospatial Library, 2008 Georeferenced image for use in a GIS.