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Randolph County
Low elevation: <360 feet above mean sea level
Place: Mississippi River
7.5' quadrangle name: Rockwood
PLSS: 3-8-8S-5W
Geology: Cahokia Alluvium in river valley
High elevation: >740 feet above mean sea level
Place: Unnamed hilltop
7.5' quadrangle name: Rockwood
PLSS: 3-29-8S-5W
Geology: Thin Vandalia till over Pennsylvanian Caseyville Sandstone
Area: 588.68 square miles
Total relief (approximate): 380 feet
Average percent slope: 1.67%
State of Illinois | Illinois Department of Natural Resources | University of Illinois