17 157 147 137 127 117 107 87 87 77 07 67 47 87 



I Ionian Drift 



Wisconsin and later drift sheets 

 I Existing glaciers and ice sheets 

 \ Quaternary lakes (Bonnevillc. Latimtan 



ami Uladal Lute .!,/) 

 J I 



107 Longitude 97 West from 87 Greenwich 77 L.L.PI 



MAP OF THE GLACIATED AREA OF NORTH AMERICA 

 From Upham's map as modified by Leverett, United States Geological Survey 



