Illinois Route 3 (IL 3) is a major north–south arterial state highway in southwestern Illinois. It has its southern terminus at Cairo Junction (about 4 mi north of Cairo) at the intersection of Interstate 57 (I-57) and U.S. Route 51 (US 51), and its northern terminus in Grafton at IL 100. This is a distance of 187.44 mi .
Illinois Route 4 is a minor north - south state highway.