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Alexander County
Low elevation: <290 feet above mean sea level
Place: Mississippi and Ohio Rivers
7.5' quadrangle name: Wyatt
PLSS: 3-32-17S-1E
Geology: Cahokia Alluvium in river valley
High elevation: >820 feet above mean sea level
Place: Dago Hill
7.5' quadrangle name: Mill Creek
PLSS: 3-10-14S-2W
Geology: Loess over Devonian dolomite
Area: 250.75 square miles
Total relief (approximate): 530 feet
Average percent slope: 1.97%
State of Illinois | Illinois Department of Natural Resources | University of Illinois