Relief shown by contours and spot heights"Based on a recompilation and recorrelation by the U.S. Department of Agriculture, and digitizing and GIS development by the Illinois State Geological Survey.""Base map compiled by Illinois State Geological Survey from data provided by the United States Geological Survey. Topography compiled from imagery dated 1958 and 1962 and planetable surveys 1961 and 1965. Planimetry derived from imagery taken 1987 and other sources. Photoinspected using imagery dated 1998.""Field checking, editing and text by M. Barnhardt, Illinois State Geological Survey.""Digital cartography by B. Stiff and J. McLeod, Illinois State Geological Survey."Includes disclaimer, index to adjoining quadrangles, text, and reference