The American Mafia, commonly known as the Mafia, Italian Mafia, Italian Mob, or the Mob in the United States, is an Italian-American criminal society. Similar to the Sicilian Mafia, the Italian-American Mafia is a secret criminal society without a formal name. Its members usually refer to it as Cosa Nostra (Italian pronunciation: [kɔza nɔstra], Italian for "our thing"). The press has also coined the name "National Crime Syndicate" to refer to the entirety of U.S. organized crime, including the Mafia. The Mafia emerged in New York's Lower East Side, other areas of the East Coast of the United States, and several other major metropolitan areas (such as New Orleans) during the late 19th century and early 20th Century following waves of Italian immigration, especially from Sicily. It has its roots in the Sicilian Mafia, but is a separate organization in the United States. Neapolitan, Calabrian, and other Italian criminal groups, as well as independent Italian-American criminals, eventually merged with the Sicilians to create the modern pan-Italian Mafia in North America. Today, the American Mafia cooperates in various criminal activities with the Sicilian Mafia and other Italian organized crime groups, such as Camorra, 'Ndrangheta, and Sacra Corona Unita. The most important unit of the American Mafia is that of a "family" as the various criminal organizations that make up the Mafia are known. Despite the name of "family" to describe the various units, succession is not necessarily hereditary, though it can be.
The Mafia is currently most active in New York City, New Jersey, Philadelphia, New England, Detroit, and Chicago; with smaller families, associates, and crews in places such as Florida, Las Vegas, Los Angeles, and Texas. There have been at least 26 cities around the United States with Cosa Nostra families, with many more offshoots, splinter groups and associates in other cities. There are five main New York City Mafia families, known as the Five Families: