Scale 1 inch
= 20 miles; this map was reduced and printed as a post card in 1972
as part of the commemoration of the Survey’s centennial.
Preliminary geological map of Minnesota.
The Geological and Natural History Survey of Minnesota.
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.