All of what is now Calumet and Manitowoc Counties was covered by ice during the last great glaciation, between 30,000 and 11,000 years ago. This bulletin explains the glacial history, interprets the deposits left behind, and portrays the distribution of the deposits on a map and cross sections. This report should be useful to planners and development agencies in making land-use decisions, to the nonmetallic mining industry to aid in locating potential sources of aggregate, and to anyone interested in the geologic history of the land on which they live.