Question: The Valachi hearings, also known as the McClellan hearings, investigated organized crime activities across America, the hearings were named after which American gangster, notable as the first member of the Italian-American Mafia to publicly acknowledge its existence,was a major government witness against the American Mafia?

Context articles: Valachi hearings
Albanian mafia
Gambino crime family
Joseph Valachi
The Valachi Papers (book)
Black Mafia
Anthony Casso
Colombo crime family
Murder, Inc.
American Mafia

The Valachi hearings, also known as the McClellan hearings, investigated organized crime activities across America and investigated leading mafia figures of the era such as Sam Giancana of Chicago.
 The hearings were initiated by Arkansas Senator John L. McClellan in 1963.
 The hearings were named after the major government witness against the American Mafia, Joseph Valachi.
The Albanian Mafia or Albanian organized crime (Albanian: "Mafia Shqiptare" ) are the general terms used for criminal organizations based in Albania or composed of ethnic Albanians.
 Albanian organized crime is highly active in Europe, North America, South America, and various other parts of the world including the Middle East and Asia.
 The Albanian Mafia participates in a diverse range of criminal enterprises including trafficking in drugs, arms, humans, and human organs.
 The Albanian criminal scenario is characterized by diversified criminal plans which, in their complexity, show one of the highest criminal capacities in the world.
 In Albania alone, there are over 15 mafia families that control organized crime.
 According to Wikileaks reports, the Albanian mafia has monopolized various international affiliations from as far east as Israel, to as far west as South America.
 These reports primarily indicate a strong connection between politicians and various Albanian mafia families.
 According to the Research Institute for European and American Studies (RIEAS), Albanian mafia groups are actually hybrid organizations (various sectors of society), often involved in both criminal and political activities.
The Gambino crime family (pronounced ] ) is one of the "Five Families" that dominates organized crime activities in New York City, United States, within the nationwide criminal phenomenon known as the Mafia (or "Cosa Nostra").
 The group, which went through three bosses between 1910 and 1957, is named after Carlo Gambino, boss of the family at the time of the McClellan hearings in 1963, when the structure of organized crime first gained public attention.
 The group's operations extend from New York and the eastern seaboard to California.
 Its illicit activities include labor and construction racketeering, gambling, loansharking, extortion, money laundering, prostitution, fraud, hijacking, pier thefts, and fencing.
Joseph Michael "Joe Cargo" Valachi (September 22, 1904 – April 3, 1971) was an American gangster, notable as the first member of the Italian-American Mafia to publicly acknowledge its existence, and credited with popularization of the term "Cosa Nostra".
The Valachi Papers is a biography written by Peter Maas, telling the true story of former mafia member Joe Valachi, a low-ranking member of the New York-based Genovese crime family, who was the first ever government witness coming from the American Mafia itself.
 His account of his criminal past revealed many previously unknown details of the Mafia.
 The book was made into a film ("The Valachi Papers"), released in 1972, starring Charles Bronson as Valachi.
The Black Mafia, also known as the Muslim Mafia, Muslim Mob, Philadelphia Black Mafia, or PBM is a Philadelphia-based African-American organized crime syndicate.
 The organization began as a small criminal collective, known for holding up neighborhood craps games and dealing in the illegal drug business, but at its height of operation until about 1975, it managed to consolidate power and control a large portion of criminal activity in various African-American neighborhoods throughout Philadelphia, the Delaware Valley, and South Jersey, including Atlantic City.
 In addition to drug trafficking, burglary, and armed robbery, the Black Mafia was also engaged in traditional organized crime activities such as extortion, racketeering, prostitution, loansharking, number running and other illegal gambling rackets.
Anthony Salvatore "Gaspipe" Casso (born May 21, 1940 in Brooklyn, New York City) is an Italian-American mobster and former underboss of the Lucchese crime family.
 During his career in organized crime, Casso was regarded as a "homicidal maniac" in the American Mafia, single-handedly killing over 40 to 50 people, and ordering as many as 100 or more murders.
 Former Lucchese captain and government witness Anthony Accetturo once said of Casso, "all he wanted to do is kill, kill, get what you can, even if you didn't earn it."
 In interviews and on the witness stand, Casso has confessed involvement in the murders of Frank DeCicco, Roy DeMeo, and Vladimir Reznikov.
 Casso has also admitted to several attempts to murder Gambino family boss John Gotti.
The Colombo crime family (pronounced ] ) is the youngest of the "Five Families" that dominates organized crime activities in New York City, United States, within the nationwide criminal organization known as the Mafia (or "Cosa Nostra").
 It was during Lucky Luciano's organisation of the American Mafia after the Castellammarese War, and the assassinations of Giuseppe "Joe The Boss" Masseria and Salvatore Maranzano, that the gang run by Joseph Profaci was recognized as the "Profaci crime family"
Murder, Inc. (or Murder Incorporated) was the name the news media gave to organized crime groups in the 1930s and 40s that acted as the enforcement arm of the Italian-American Mafia, Jewish mob, and connected organized crime groups in New York and elsewhere.
 The groups were largely composed of Italian-American and Jewish gangsters from the Brooklyn neighborhoods of Brownsville, East New York, and Ocean Hill.
 Originally headed by Louis "Lepke" Buchalter, and later by Albert "The Mad Hatter" Anastasia, Murder, Inc. was believed to be responsible for between 400 and 1,000 contract killings, until the group was exposed in the early 1940s by former group member Abe "Kid Twist" Reles.
 In the trials that followed, many members were convicted and executed, and Abe Reles himself died after "falling out of a window".
 Thomas E. Dewey first came to prominence as a prosecutor of Murder, Inc. and other organized crime cases.
The American Mafia (commonly shortened to the Mafia or Mob) or Italian-American Mafia, is a highly organized Italian-American criminal society.
 The organization is often referred to by members as Cosa Nostra (] , "our thing") and by the government as La Cosa Nostra (LCN).
 The organization's name is derived from the original ""Mafia"" or "Cosa nostra", the Sicilian Mafia, and it originally emerged as an offshoot of the Sicilian Mafia; however, the organization eventually encompassed or absorbed other Italian-American gangsters and Italian-American crime groups (such as the American Camorra) living in the United States and Canada that are not of Sicilian origin.
 It is often referred to as the Italian Mafia or Italian Mob, though these terms may also apply to the separate yet related organized crime groups in Italy.