I will be driving through the area tomorrow/Saturday - I'll check it out to make sure.
NOTE:
https://cote.transportation.org/interstate-control-cities/ This is the AASHTO official list of control cities for the Interstates. Rockford does not appear anywhere on I-90's list. Thus either Janesville or Madison would
technically be the correct cities to put in. Note that this list is both incomplete and poorly written.
294 is a grey area since it is a half-belt.
Keep in mind that ISTHA is doing their own thing - hence Rockford. IDOT, however?
Many DOTs are not following this list - I don't believe it's a requirement either.
IDOT has mainline cities set as the long distance version for on the highway and short-distance for junctions. Incomplete list:
24: Long: Nashville, "To Interstate 57"; Short: Paducah, Vienna(?)
39: Rockford, Rochelle, Puru-LaSalle and Bloomington (Late add by IDOT int the 1990s)
57: Long: Memphis, Chicago; Short: "Interstate 80", Kankakee, Champaign-Urbana, Effingham, Mt Vernon, Cairo
64: Long: St Louis, Louisville; Short: East St Louis, Mt Vernon
70: Long: St Louis, Indianapolis; Short: East St Louis, Effingham
72: Hannibal, Jacksonville, Springfield, Decatur, Champaign-Urbana (This route does not follow the others rules as it was a late add in the 90s)
74: Long: Moline-Rock Island, Peoria, Indianapolis; Short: Gailsville, Bloomington, Champaign-Urbana
80: Iowa, Chicago, Indiana; Short: Moline-Rock Island, Peru-La Salle, Joliet
88: Aurora, DeKalb, Rochelle, Rock Island (This is mostly ISTHA and it was a late add in the 90s)
90: Wisconsin, Rockford, O'Hare, Chicago, "Indiana Toll Rd"
94: Long: Milwaukee, Chicago, Indiana; Short: Rockford, O'Hare
The 3dis have a little bit of a different rule based on where they are.
Around Chicago - IDOT like very much to use "Suburbs", ISTHA a bit less so. St Louis metro does use cities (Memphis south on 255, "Interstate 270" north, KC west on 270, Indy East)
280 does the same as 80.
155 just has Lincoln and Peoria.
EDIT: I didn't mention 180 for obvious reasons.