Here is a delightful image of downtown Chicago from the 1960s.
This is from Chuckman's collection.
Hopefully you noticed the train yard in the lower left hand side. It is
gone, replaced with Millennium Park, which you can see in the modern
photo in the upper part.
Here is a similar view today
This is from the opposite side of Grant Park looking north. Can you believe I can't find a modern equivalent of the 1960s camera angle? If you find one please send it my way.
And here is the downtown skyline, this time from 1929 and again you can see the rail yards lurking in the corner.
More views of the old train yard.
Is that discoloration on the nearby buildings soot from pollution, age of the photo, or something else?