Continuity: The results of Rothstein's first card deal on the table are not visible subsequently.
Factual errors: Vincent "Mad Dog" Coll was shot by Dutch Schulz's hitmen in a cafe; Lucky Luciano had nothing to do with it.
Anachronisms: At that time, the game of choice would have been 5-card stud. 7-card stud was almost unknown.
Factual errors: In real life, Benjamin Siegel despised the nickname "Bugsy" to the point of inflicting bodily harm upon anyone calling him by it, yet has no problems being addressed by it several times throughout the movie.
Anachronisms: The Internal Revenue Service is mentioned twice as having investigated income tax evasion. Before 1953 the IRS was the "Bureau of Internal Revenue"; it was changed to Internal Revenue Service to emphasize "service" to taxpayers.
Factual errors: In real life, after the assassination of Joe 'The Boss' Masseria, one of the gunmen, (reputedly Ben Siegel), placed an Ace of Spades playing cards between the dead man's fingers. However, the film makes no mention of this fact.
Factual errors: The other boss prominent in the 'Castellammarese War', was Salvatore Maranzano. However, in the movie his name has been changed to Salvatore Faranzano played by Michael Gambon as a mob boss who had terrorized Luciano's neighbourhood for over 15 years. The real Maranzano was only 34 years old when he was shot and stabbed to death. The movie depicts the fictional 'Farenzano' is a much older man who was thrown from an upper story window to his death.