In the episode "1969," one of my all time favorite episodes, after the team gets on the bus in Colorad to go to New York along Route 66, a map follows their progress eastward and uses a blend of a red line covering their progress on the road map and fading just enough to show photos and scenes of them as they move along in their journey eastward.

As the map shows them passing by Chicago, the map fades a bit and we see a shot of Chicago's famous Sear's Tower thus giving us a sense as to where they are. A definite Chicago icon to be sure.

But, since the show is about them traveling back in time because of a solar flare messing with their going through the stargate and they find themselves back in 1969, this photo of the Sear's Tower could not have happened since the Sear's Tower was not even started until the early '70s.