I found some cool stuff for my birth state of IL! Among the following are:
The 1966 relocation of I-494 from Lake Shore Drive to the Crosstown Expressway, with full freeway interchanges at the Kennedy-Edens split, Eisenhower, Southwest (Stevenson) and Dan Ryan Expressways; half-diamonds at Belmont Avenue (southbound), Diversey Avenue (northbound), Washington Street (southbound), Madison Street (northbound), Kedzie Avenue (westbound), Columbus Blvd (eastbound) and Halsted Street (eastbound); and full diamonds at Milwaukee Avenue, North Avenue, Chicago Avenue, 16th Street, 31st Street, Archer Avenue, 63rd Street, Pulaski Road and Ashland Avenue. Also, the orientation would change from N-S to E-W between Archer Avenue and 63rd Street.
Various 1950s applications for US 58 that would've run along parts of US 460 and US 51.
A 1974 application for I-53 that would've run from I-55 to I-80 and included what is now I-180.
A 1981 application for US 251 that would replace US 51, which was being relocated to a new freeway (now I-39). This route was eventually given an IL state route designation of the same number.
A 1990 application for I-37 that would run from I-55 at Lincoln to I-74 at Morton; it is now I-155.