Starting from the twenties, the underworld in the United States of America and consequently the Cosa Nostra changed drastically. The cause of all this was to be attributed to Prohibition. In addition, as regards the American mafia, an important contributing cause should not be overlooked, namely the strong repression of the fascist regime against the Italian mafia, which took place in the same period of time. In fact, this led to the flight of many Sicilian mafia to the new continent. The era of so-called Prohibition comes into force in the United States with the approval of the eighteenth amendment to the American constitution. According to this new law, passed in 1919, the production and distribution and retail sale of any alcoholic beverage was prohibited in the United States of America, essentially the offender committing a federal crime.