The city has launched a new mapping tool that has aerial photos from as long ago as 1958. I could spend hours tooling around and showing you stuff, but you should load up the tool and enjoy it yourself. Click the "I Want To" button at the top and choose "historical aerial photos".
As a taste of what you can find - here's what the Museum of Nature (or Museum of Man at the time?) looks like in 1958 vs. 2011. I never new the eastern pathway through the (diminished) park was originally part of a circle. Click to embiggen.
If you step through each year you can see the progression of more and more parking at the museum from none, to almost total. So sad.
What did you find?