The location for the "dungeon under the speakeasy" was an ACTUAL speakeasy back in the 1920s. The secret room was hidden under the Star Hotel in Marcus Hook, PA - a port frequented by sailors back in the day. The original hidden stairways and plastered walls can be seen in the movie.
After a fruitless nationwide search for an authentic 1930s police car, the car wrangler came across a "barn find" of a 1931 Ford Model A that had not been started for 15 years. The rapid 1-month restoration was completed just in time for the first day of shooting. Miraculously, the 85-year old car ran for 7-straight hours without stalling or overheating.