Dutch says to Lucky: "I'm going to the library. I'm going to take out that book "How to #*%& friends and irritate people." Here he is parodying the popular self-help book by Dale Carnegie, "How to Win Friends and Influence People." Published in 1936 and an instant best-seller, the book would have been discussed widely in social circles during the time of the film, hence why Lucky smirked when he heard the joke.
An old friend of the real Lucky Luciano allowed Andy Garcia to wear Lucky's pinkie ring for one scene. You can see it when Lucky gives Thomas Dewey the bribe money at the whorehouse, when the prostitute takes the cigar out of Lucky's hand.
Although Ellsworth "Bumpy" Johnson, Dutch Schultz, Lucky Luciano, and Stephanie St. Clair existed in real life, the movie is fictional and only loosely based on incidents in their lives during this time period. Many other characters, including Francine Hughes, Captain Foley, and Calvin, are wholly fictional.
Actor Clarence Williams III who plays the character Bub Hewlett, a rival of Ellsworth "Bumpy" Johnson's, would go on to portray Johnson in the first few scenes of American Gangster (2007) 10 years later.
In Luciano's close ups, his right eye is not open as much as the left. On many historical pictures of the real Lucky Luciano his right eye is partially closed as well. This was due to a knife injury during a 1929 abduction by unknown assailants that damaged muscles in his right cheek that prevented his eye from working properly.
In Lucky Luciano's introductory scene, in which he pulls up to Dutch Schultz's office in a limo, he gets out of the car and passes a pet Chihuahua dog to one of his men saying "Take Bambi for a walk." In real life, Lucky Luciano did own a dog called Bambi. However, he bought the dog in Sicily after he'd been deported from the United States in 1946. Luciano had named the dog after the movie Bambi (1942). Yet in this movie, he is seen with the dog in the 1934-1935 time period, before the release of that movie and before he actually bought the dog.
The film's portrayal of Tom Dewey, as a corrupt sleazebag who regularly took bribes from gangsters, was widely criticized by those who knew Thomas E. Dewey. The real Dewey was known to be the most honest and incorruptible member of the establishment, during his stints as District Attorney and then New York Governor. It was this good reputation that got him within a hair's breadth of being elected United States President in 1948.
Four actors who had uncredited parts in this film: Andy-John who played Driver #4, Leon 'Lee' Fuller who played Vagrant, Joseph Luis Caballero who played Hector and Dominic Paolo Testa who played Prostitute Patron, co-starred again in uncredited parts the same year in another film, Home Alone 3 (1997). Andy-John as 'Police Officer #1', Fuller as a 'Banker', Caballero as a 'Security Guard' and Testa as a 'Airline Passenger'.
The trivia items below may give away important plot points.
Although it is not specifically mentioned in the film, the reason Dutch Schultz was killed was because he planned on assassinating prosecutor Thomas E. Dewey. Dutch was under indictment for racketeering and tax evasion charges and was such a volatile gangster that he was willing to risk unbearable heat from law enforcement to kill Dewey. However, when the organized crime syndicate - led by Lucky Luciano, Longy Zwillman and others - learned what Dutch was planning, Zwillman (who actually disliked violence) ordered his death, which was affirmed by the syndicate. Schultz was shot by two of Zwillmen's trigger men, and died in the hospital after he contracted a staph infection as the result of his gunshot wounds.