Illinois State Route 23 runs north-south in Western Mc Henry County. It runs from the De Kalb/Mc Henry County Line, near Riley, to U.S. Rt. 14, near Harvard. IL St Rt 23 passes through the following town in Mc Henry County. Marengo IL St Rt 23 is not multi-plexed in Mc Henry County. IL St Rt 23 crosses the following highways in Mc Henry County. Interstate 90, (Addams Tollway) near Riley.
A BGS on EB I-90. A BGS on WB I-90. SB IL St Rt 23 south of Harmony Road. A BGS on SB IL St Rt 23. SB IL St Rt 24 north of Coral Road. SB IL St Rt 23 north of U.S. Rt. 20. A junction marker on WB IL St Rt 176. SB IL St Rt 23 at IL St Rt 176. SB IL St Rt 23 near 3rd in Marengo. NB IL St Rt 23 in Marengo. SB IL St Rt 24 north of Marengo. NB IL St Rt 23 near the Kishwaukee River. SB IL St Rt 23 at Kishwaukee Valley Road. SB IL St Rt 23 at Olbrich Road. NB IL St Rt 23 near Hartland. The northern end of IL St Rt 23 near Harvard. The northern end marker.
