In Illinois, the maximum speed limit is 65 mph on rural interstate highways where posted. The maximum speed limit on most other highways is 55 mph. You may drive at the maximum allowable speed only under safe conditions. In order to avoid car accidents, it is also important to take care when approaching and crossing an intersection, going around a curve, approaching the top of the hill, or traveling on a narrow and winding roadway.
For more information on driving safely in Illinois.