A good Chicago movie
Chicago should be listed as one of the stars of this film, since so much depends on the North-side neighborhood feel.
I moved away from there 12 years ago but just saw the movie today. I was trying to figure out the location of the main neighborhood. It had to be at one of the rare neighborhoods where there's a fork in a "L" line (you can see two trestles in the background at John Candy's house several times).
My dad worked for the CTA for years and one of the control towers used to be on Clark St. where the Ravenswood line branches off to the west. Thanks to Google maps, I found the spot: near the corner of Clark and Roscoe (you can see a Roscoe St. sign briefly in the film). If you zoom in on the hybrid Google map, you can easily see the corner near where the house was located.
Also, this a rare memento of the old Comiskey Park. There's a nice scene shot inside the empty park, with the fireworks going off. In the establishing shot, you can see the new park being built (on the right side of the screen). Not long after, Comiskey would be a pile of rubble.