Contributed by: Michael Haxton
In one scene Eliott Ness is in a warehouse with crates of illegal Canadian Whisky. The crates have the red maple leaf on them. The current Canadian Flag, with the red maple leaf, was not brought into existence until 1964.
When Kevin Costner goes to see Sean Connery at his apartment to ask for help when he opens the door to Costner, Sean Connery's top button on his shirt is done up but later on in the room it comes undone and done up and then undone again oops!
In numerous scenes, the municipal flag of the City of Chicago is shown as having four stars. The fourth star on the flag, was not added until 1933, 3 years after the movie's 1930 time frame.
Contributed by: Mike Scott
In the movie, Frank Nitti dies by falling from a roof top after battling Elliot Ness. In reality, Nitti didn't die until several years later. He became the "front man" for the Chicago Outfit in 1932 after Al Capone went to prison for Tax Evasion but committed suicide while under indictment in 1943.