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Crawford County
Low elevation: <410 feet above mean sea level
Place: Wabash River
7.5' quadrangle name: Russelville
PLSS: 2-21-5N-10W
Geology: Cahokia Alluvium
High elevation: 640 feet above mean sea level
Place: Unnamed hilltop
7.5' quadrangle name: Flat Rock
PLSS: 2-35-6N-12W
Geology: Illinois Vandalia till upland over Pennsylvanian Mattoon Formation?
Area: 440.97 square miles
Total relief (approximate): 230 feet
Average percent slope: 0.91%
State of Illinois | Illinois Department of Natural Resources | University of Illinois