April 20, 2008: Former sign at a road intersecting I-172 in Adams County, Illinois.
I-172 is an interstate spur in far western Illinois connecting Quincy to Interstate 72. For decades, I-72 ended where I-172 began, until a new bridge across the Missouri River was built in Hannibal.
But for at least a decade, signs on the roads intersecting I-172 did not mention Quincy, instead mentioning Mount Sterling, Illinois, and Keokuk, Iowa. (The above is dated November 2002; replacements were up by October 2012.) The interstate reaches neither of those cities and in fact, they’re in two very different directions. Keokuk is the next largest city to the north, via IL 96; Mount Sterling is to the east, via US 24. In that way, I-172 was less a route to Quincy than a bypass of Quincy from I-72 to the routes to get to those cities.
Illinois has replaced all the signs in Clearview. Carthage and Macomb are the new destinations, which make much more sense from a corridor standpoint. Illinois has been upgrading an assortment of roads to four lanes between Galesburg and Quincy — US 34, US 67, US 136, and IL 94. Illinois wants to encourage traffic to use those highways (along with I-74 and I-88), and then US 36, between Chicago and Kansas City. The last part in the “CKC” corridor, the Macomb bypass, could be completed this year.
The state even went so far as to create a new number, 110, specifically to overlap the whole corridor. As far as I can tell, no one uses the number in an everyday manner, not even the state — the number shield is tacked on to larger signs at interchanges and never included in the main part. But Illinois is so into this “corridor” thing that there’s another number, 336, overlapping 110 and the previously-numbered routes between the north end of I-172 and Macomb. That’s the one that gets on the big signs. Illinois could’ve given more prominence to 110 and not dealt with 336 at all, but then, efficiency isn’t the state’s strong suit.
Although Keokuk never connected to I-172, for a time the city got more respect on signs in Illinois than it did in Missouri, which leaves it out of every interchange on the Avenue of the Saints until US 61 splits from the four-lane near the Iowa border.