Interstate 172 is a spur northward to the Quincy area from Interstate 72, in west-central Illinois. It is also the start of an alignment that continues as a rural expressway northeastward toward Carthage and Macomb, known as Illinois 336. Interstate 172 is a very lightly-traveled freeway up to Quincy, splitting from Interstate 72, which continues west from Springfield and Jackson to Hannibal, Missouri.
Exits on this page will be listed in increasing order from south to north, in accordance with the nationally-recognized standard for mile numbering on north-south highways.
The southern beginning of Interstate 172 is at Interstate 72 just east of Hannibal, Missouri, along the Adams/Pike County line in Illinois. The southbound carriageway continues to eastbound Interstate 72 toward Pittsfield and Springfield, whereas the ramp to Interstate 72 west toward Hannibal is labeled "Exit 0":
Exit 2 is to the southern beginning of Illinois 57, a surface road to Marblehead and downtown Quincy:
Exit 10 is for Illinois 96, leading to Payson and to 36th Street in Quincy:
Exit 14 is for Illinois 104, known as Broadway, the main east-west street out of downtown Quincy:
Exit 15 is for Columbus Road and Wismann Lane in Quincy:
Exit 19 is for US Route 24 signed as a way to Illinois 96, Mount Sterling, and Keokuk, Iowa (which it ISN'T), and this exit marks the northern terminus of Interstate 172. The highway continues north as a rural expressway labeled as Illinois 336.