Illinois Route 23
|Maintained by IDOT|
|Length:||126.17 mi (203.05 km)|
|Existed:||November 5, 1918 – present|
|South end:||Historic US 66 / IL 116 in Pontiac|
| Historic US 66 in Pontiac
I-55 in Pontiac
US 6 / IL 71 in Ottawa
I-80 in Ottawa
US 52 in Serena
US 34 in Leland
US 30 in Waterman
US 20 in Marengo
|North end:||US 14 in Harvard|
|Counties:||Livingston, LaSalle, DeKalb, McHenry|
Illinois Route 23 is a north–south state highway in northern Illinois. It runs from Illinois Route 116 in Pontiac north to U.S. Route 14 south of Harvard. This is a distance of 126.17 miles (203.05 km).
The road starts near downtown Pontiac and runs as the main highway north, intersecting with Interstate 55 and former U.S. Route 66. From this point, Illinois 23 continues as a 2-lane highway, turning west and running through Cornell. After that, it turns back north to travel through the middle of Streator, where the route splits to follow two different one-way streets (Park Street and Bloomington Street). Route 23 continues through Grand Ridge to Ottawa, where the road follows 1st Ave and State street, to form a concurrent with Illinois Route 71—Illinois 71 across the Illinois River. The highway once again splits into two one-way streets (Columbus and LaSalle Streets) through downtown Ottawa, until a block south of its junction with U.S. Route 6, where Illinois 71 departs toward the east.
North of Ottawa, Illinois 23 has a full diamond interchange with Interstate 80. This is the last full interchange Illinois 23 has south of its terminus at Harvard. Illinois 23 has two additional concurrencies with U.S. Route 34 and U.S. Route 52, though no notable cities are present between Ottawa and DeKalb. Illinois 23 runs under Interstate 88 with no intersection, though access is available via Fairview Drive to two parallel roads with interchanges (Peace Road and Annie Glidden Road). Between DeKalb and Sycamore, Illinois 23 has four lanes. In Sycamore, Illinois 23 briefly overlaps Illinois Route 64. After one final concurrency at Illinois Route 72 near Genoa, Illinois 23 travels over Interstate 90 with no interchange and no nearby access. It runs through Marengo and terminates south of Harvard at U.S. Route 14.
Illinois 23 was established in 1918 as one of the original 46 SBI routes. The routing of Illinois 23 has not changed since its establishment.
Plans are in the works to build an interchange where Illinois Route 23 crosses the Jane Addams Memorial Tollway (Interstate 90). The overpass is scheduled to be replaced in 2017, and the ramps could follow. Building an interchange at IL-23 would open up a faster route to Marengo and Genoa, as well as close a 17-mile gap on I-90 between the Genoa Road and US 20 exits.
|Livingston||Pontiac||0.0||0.0||IL 116 (Howard Street) / Historic US 66 south||South end of Historic US 66 overlap|
|0.4||0.64||Historic US 66 north||North end of Historic US 66 overlap|
|||2.6||4.2||I-55 – Joliet, Bloomington|
|||7.4||11.9||IL 170 north|
|La Salle||Streator||26.0||41.8||IL 18 (Bridge Street, Main Street)|
|Ottawa||41.3||66.5||IL 71 west (Hitt Street)||South end of IL 71 overlap|
|Illinois River||41.4||66.6||Ottawa Bridge|
|Ottawa||42.4||68.2||US 6 / IL 71 east (Norris Drive)||North end of IL 71 overlap|
|43.9||70.7||I-80 – Joliet, Moline, Rock Island|
|||50.4||81.1||US 52 west (North 37th Road)||South end of US 52 overlap|
|||52.4||84.3||US 52 east (North 38th Road)||North end of US 52 overlap|
|||59.5||95.8||US 34 west (Walter Payton Memorial Highway)||South end of US 34 overlap|
|||63.6||102.4||US 34 east (Walter Payton Memorial Highway)||North end of US 34 overlap|
|DeKalb||Waterman||74.3||119.6||US 30 (Lincoln Street)|
|DeKalb||85.4||137.4||IL 38 (Lincoln Highway)|
|Sycamore||90.8||146.1||IL 64 west (State Street)||South end of IL 64 overlap|
|91.4||147.1||IL 64 east (State Street)||North end of IL 64 overlap|
|Genoa||98.9||159.2||IL 72 west (Main Street)||South end of IL 72 overlap|
|||100.9||162.4||IL 72 east||North end of IL 72 overlap|
|McHenry||Marengo||112.2||180.6||US 20 (General Grant Highway)|
|112.7||181.4||IL 176 (Telegraph Street)|
|Harvard||126.17||203.05||US 14 (Division Street)|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
- In downtown De Kalb, Route 23 (the main north–south street) intersects as 4th Street with Illinois Route 38 (the main east–west street) at a railroad crossing, as two Union Pacific tracks pass through the crossing. Trains routinely bring traffic in De Kalb to a halt.
- Carlson, Rick. Illinois Highways Page: Interstates in Illinois. Last known update March 15, 2006. Retrieved March 21, 2006.
- Illinois Technology Transfer Center (2007). "T2 GIS Data". Retrieved 2007-11-08.
- Craver, Kevin. "McHenry County Board adds I-90/Route 23 interchange in Marengo to transportation plan". Northwest Herald. Retrieved 13 April 2016.
- Google Maps, 
Route map: Google