Revealing mistake: Near the end when Ace gets into his Cadillac, in the first shot facing the front of the car, there is a protective glass in front of Ace (the same width as the windshield) with the dashboard in between that glass and the windshield. Note the vertical edge of the glass is visible at the right side, and the rearview mirror's sticker on the windshield casts a shadow onto the second glass. During the stunt, the flames on the dashboard are between the glass shield and the windshield, keeping the actor safe from harm. (02:46:05)
Answer: Frank Rosenthal (the basis for Sam Rothstein) and Tony Spilotro (the basis for Nicky Santoro) were both from Chicago, so that is likely "back home".