The most famous criminal organization in the United States has its origins in medieval Sicily, where wealthy landowners once hired groups of bandits to guard their estates. Eventually, the bandit gangs (see entry under 1980s—The Way We Lived in volume 5) grew so strong they were able to challenge the established authorities in both Sicily and Italy. Although most Mafia members are of either Sicilian or Italian descent, they represent only a small percentage of their respective cultures. Many Americans of Italian or Sicilian heritage resent the popular culture stereotypes that suggest that all those sharing their ethnic heritage are criminals.

The Mafia came to America through immigration in the 1880s and was well established in the United States by the following decade. Some experts distinguish between the Sicilian Mafia and its American counterpart by calling the latter the Cosa Nostra (an Italian phrase meaning, literally, "our thing...