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Calhoun County
Low elevation: <420 feet above mean sea level
Place: Illinois and Mississippi Rivers
7.5' quadrangle name: Grafton
PLSS: 4-6-13S-1E
Geology: Cahokia Alluvium, river valley
High elevation: >815 feet above mean sea level
Place: unnamed hilltop
7.5' quadrangle name: Foley
PLSS: 4-14-11N-2W
Geology: Providence Moraine, Wisconsin end moraine
Area: 280.66 square miles
Total relief (approximate): 395 feet
Average percent slope: 3.55%
State of Illinois | Illinois Department of Natural Resources | University of Illinois