Goofs:
Anachronisms: The Chicago flag appears throughout the movie, but the flag was not in existence in 1929-30. The 4 stars on the flag represent 1) Fort Dearborn, 2) The Chicago fire, 3) The World Columbian Exposition of 1893, and 4) The Century of Progress, World's Fair of 1933. The flag could not have existed then as the event represented by the 4th star had not yet happened. (more)

Trivia:
Kevin Costner, Sean Connery and Andy Garcia engaged in police tactic and weapons training for the film - from the 1950s. (more)

Filming Locations:
40 miles south, Great Falls, Montana, USA (more)

Quotes:
[first lines]
Title Card: 1930. Prohibition has transformed Chicago into a City at War. Rival gangs compete for control of the city's billion dollar empire of illegal alcohol, enforcing their will with the hand grenade and tommy gun. It is the time of the Ganglords. It is the time of Al Capone.
Reporter: [to Al Capone] An article, which I believe appeared in a newspaper, asked why, since you are, or it would seem that you are, in effect, the mayor of Chicago, you've not simply been appointed to that position.
(more)

Awards:
Won Oscar. Another 9 wins & 11 nominations (more)