Origins: The Black Hand

Mafia groups in the United States first became influential in the New York City area, gradually progressing from small neighborhood operations in poor Italian ghettos to citywide and eventually international organizations. The American Mafia started with La Mano Nera, "The Black Hand", extorting Italians (and other immigrants) around New York city. Black Hand gangsters would threaten them by mail if their extortion demands were not met. The threats were sometimes marked with a hand-print in black ink at the bottom of the page. As more Sicilian gangsters immigrated to the U.S., they expanded their criminal activities from extortion to loan-sharking, prostitution, drugs and alcohol, robbery, kidnapping, and murder. Many poor Italian immigrants embraced the Mafia as a possible way of gaining power and rising out of the poverty and anti-Italianism they experienced in America.

Giuseppe Esposito was the first known Sicilian Mafia member to emigrate to the United States. He and six other Sicilians fled to New York after murdering eleven wealthy landowners as well as the chancellor and a vice chancellor of a Sicilian province. He was arrested in New Orleans in 1881 and extradited to Italy.

New Orleans was also the site of the first Mafia incident in the United States that received both national and international attention. On October 15, 1890, New Orleans Police Superintendent David Hennessey was murdered execution-style. Hundreds of Sicilians were arrested, and nineteen were eventually indicted for the murder. An acquittal followed, with rumors of bribed and intimidated witnesses. The outraged citizens of New Orleans organized a lynch mob and proceeded to kill eleven of the nineteen defendants. Two were hanged, nine were shot, and the remaining eight escaped.
In the 1910s and 1920s in New York City, the Sicilian Mafia developed into the Five Points Gang.

The rising: the Prohibition

Charles "Lucky" Luciano , one of the most famous American bosses
Mafia activities were restricted until 1920, when they exploded because of the introduction of the prohibition. Al Capone's Syndicate in the 1920s ruled Chicago.

By the end of the 1920s, two factions of organized crime had emerged, causing the Castellamarese war for control of organized crime in New York City. With the murder of Joseph Masseria, the leader of one of the factions, the war ended uniting the two sides back into one organization now dubbed Cosa Nostra . Salvatore Maranzano, the first leader of American Mafia , was himself murdered within six months and Charles "Lucky" Luciano became the new leader. Maranzano had established the code of conduct for the organization, set up the "family" divisions and structure, and established procedures for resolving disputes. Luciano set up the "Commission" to rule their activities. The Commission included bosses from six or seven families.

After-war

In 1951, a U.S. Senate Committee, led by Democratic Tennessee Senator Estes Kefauver, determined that a "sinister criminal organization", with ties to the USSR, also known as the Mafia operated around the United States.

In 1957, the New York State Police uncovered a meeting of major American Cosa Nostra figures from around the country in the small upstate New York town of Apalachin. This gathering has become known as the Apalachin Conference. Many of the attendees were arrested and this event was the catalyst that changed the way law enforcement battles organized crime.
In 1963, Joseph Valachi became the first American Cosa Nostra member to provide a detailed look at the inside of the organization. Having been recruited by FBI Special Agents, and testifying before the US Senate McClellan Committee, Valachi exposed the name, structure, power bases, codes, swearing-in ceremony, and members of this organization. All of this had been secret up to this point.

Today Cosa Nostra is involved in a broad spectrum of illegal activities. These include murder, extortion, drug trafficking, corruption of public officials, gambling, infiltration of legitimate businesses, labor racketeering, loan sharking, prostitution, pornography, tax fraud schemes, and most notably today, stock manipulation schemes.

Union corruption

Jimmy Hoffa
In the mid-20th century, the Mafia was reputed to have infiltrated many labor unions in the United States, notably the Teamsters, whose president Jimmy Hoffa disappeared and is widely believed to have been murdered. In the 1980s, the United States federal government made a determined effort to remove Mafia influence from labor unions.