Low Elevation
< 650 feet above mean sea level
Low Place
Rock River
Low Quad Name
Grand Detour
Low PLSS
4-8-22N-9E
Low Geology
Cahokia Alluvium, river valley
High Elevation
> 1020 feet above mean sea level
High Place
Southeast branch of Hardpan Ridge
High Quad Name
Forreston North
High PLSS
4-3-25N-8E
High Geology
Thin Illinois Ogle till over Silurian dolomite
Area
757.12 square miles
Total Relief
370 feet
Percent Slope
1.71%