1943. Geological Survey (U.S.). Contour interval 10 feet.;"Surveyed in 1929 and 1939-1940"; (W 88⁰15ʹ00ʺ--W 88⁰00ʹ00ʺ/N 39⁰15ʹ00ʺ--N 39⁰00ʹ00ʺ);Relief shown by contours and spot h... Geological Survey (U.S.) and Geological Survey Division (Urbana, Ill.).