I consulted with my local tree expert, and she thinks these trees outside my office window are American Sycamores. There seem to be quite a few in Highland Park.
I was attracted to them because of the round seed balls.
The above is a photo of the seed ball, before we got white snow now gracing Highland Park.
The trunks have this distinct peeling bark. This particular tree is on Abbott Street.
Same tree as above, but the sky was bluer.