Illinois Route 23 runs north-south in north-central Illinois, a little east of Illinois's exact center. Illinois Route 23 connects many different communities, serving as the main north-south route in DeKalb, eastern LaSalle, and western McHenry Counties. It cuts into Livingston County, too, to end at Pontiac.
The northern end of Illinois 23 is at US Route 14 in Harvard, about seven miles south of the Wisconsin border:
Illinois 23 enters Marengo and meets the western end of Illinois 176: