The best-known organized crime group in the U.S. is the mafia, or the Cosa Nostra. The word Mafia is actually an Italian acronym for the phrase "Death to the French' Cry the Italians."
The Mafia originated as groups of fighters recruited by Sicilian landowners in the early 19th century, in reaction to Napoleanic invasions of southern Italy and Sicily.

Eventually, selected groups of the Mafiosi became so powerful that they discarded their fighting pride to overthrow their employers and gain considerable power and wealth. Enough in fact, that they were able to gain political office via terrorist tactics.
After taking control of the law enforcement agencies to legally carry arms, they were suppressed by the Italian government, forcing many of the Mafia leaders to emigrate to the U.S.
In Sicily, the Mafia was finally suppressed by the fascist Italian government during the 1920s.
In the United States, however, the Mafia was gaining substantial power. Prohibition provided an excellent market opportunity, through which the corrupt Italians acquired wealth and power. The organization developed a virtual monopoly on illegal gambling, and significantly penetrated the legal gambling market as well.
The Mafia today comprises a number of semi-autonomous crime families, the heads of which sit on various councils. Membership is by initiation, and leardership is generally at least partially hereditary-unless there is a coup.