I love historian J.R. Schmidt's "Then and Now" series on his Chicago History Today blog. Mostly he posts photos he took as a kid (late 1940s through early 1960s) and contrasts them with contemporary photos.
Then, recently, I came across this photo from a location just a couple of blocks from me that photographer Bob Rehak took during an arson epidemic on 22 April 1976:
Here's the same location today:
Rehak's other photos from the era are incredible. Uptown was in a different universe 45 years ago.