The southern endpoint of US 14 is in Chicago at Broadway and Foster Avenue. For several years there was one marker on Broadway that missing the center point of its shield. It was on Broadway just south of the intersection with Ridge and Bryn Mawr avenues. The sign was there at least until 2002; on a return visit to the area in 2006, I found that the shield had been replaced by a normal US shield.
That wasn't not all, though. Take a look to the right at this. IDOT (the Illinois Department of Transportation) apparently got the sign blank turned around for this marker on Harlem Avenue in Niles, just over the city line from Morton Grove.
The photograph in Niles was taken in December 1998.