Although Illinois has been nicknamed the “Prairie State,” many parts of it are hilly and scenic. The idea of large areas of the state being nothing more than broad, flat prairies has come about because the major highways have been built to take advantage of the comparatively low, gently rolling landscape rather than the rougher more scenic areas.
Physiography is the study of the creation and gradual change of land surface forms (the landscape). Thus, the land surface as we see it today in each of the physiographic provinces ([fig. 1]) has had a particular history of development.
Illinois is about 385 miles long from north to south and about 218 miles wide. It has an area of 55,947 square miles. The average elevation of the state is about 600 feet above sea level. Charles Mound, however, in the northern part of Jo Daviess County in extreme northwestern Illinois, has an elevation of 1,241 feet above sea level and is the highest point in the state.
Cheap water transportation is available to Illinois industry through Lake Michigan, the Illinois Waterway, and the Mississippi, Ohio, and Wabash Rivers. These major rivers of Illinois collect the surface drainage of the state from a network of about 500 streams.
WHAT IS THE EARTH MADE OF BENEATH THE GROUND SURFACE?
The earth is made of a large number of different rocks and minerals (limestone, sandstone, shale, coal, iron, granite, and many others). These materials are divided into three zones: core, mantle, and crust ([fig. 2]).
Figure 1—Physiographic provinces of Illinois.
DRIFTLESS AREA WISCONSINAN MORAINES ILLINOIAN TILL PLAIN MISSISSIPPI RIVER WABASH RIVER SHAWNEE HILLS OHIO RIVER
