after 1892
Geological Survey (U.S.)
1967
Willman, H. B.
circa 1935
Illinois State Geological Survey
1966
February 1969
Northeast Illinois Planning Commission
1948
late 1960s
1973
1974
1933
November 1977
1922 – 1954
1927
Geological Survey (U.S.), Illinois Department of Registration and Education
1960 – 1973
1960
1965
May, V. Jeff, Allen, Howard E.
1959 – 1960
1911
1969