1. Geologic map of Precambrian rocks of parts of Iron Mountain and Escanaba 30ʹ x 60ʹ quadrangles, northeastern Wisconsin and adjacent Michigan Yale Public content 1993. 2002-06-01T04:00:00Z. 2020-10-16T18:52:49Z. Geological Survey (U.S.). The Survey ; For sale by Map Distribution. English. Public. Michigan and Wisconsin. Precambrian.