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Washington County
Low elevation: <385 feet above mean sea level
Place: Kaskaskia River
7.5' quadrangle name: Venedy
PLSS: 3-30-1S-5W
Geology: Cahokia Alluvium in river valley
High elevation: ~583 feet above mean sea level
Place: Unnamed hilltop
7.5' quadrangle name: Oakdale
PLSS: 3-16-3S-4W
Geology: Hagarstown ridge
Area: 557.82 square miles
Total relief (approximate): 198 feet
Average percent slope: 0.71%
State of Illinois | Illinois Department of Natural Resources | University of Illinois