William C. Alden. (1903). Map of a portion of southeastern Wisconsin at the time of the formation of the second gravel terrace, showing the relations of the Lake Michigan Glacier, including the Delevan Lobe, to the Green Bay Glacier and of the moraines and attendant outwash deposits to the earlier drift deposits. U.S. Geological Survey. https://geodata.wisc.edu/catalog/cc16a296-2bd9-455a-a0d8-3fc301c75b10