The Barzini family was founded by Giuseppe Mariposa in 1920s and replaced by Emilio Barzini in 1934, who expanded his territories apart from Brooklyn areas included areas of Manhattan and Queens, while completely controlled Staten Island. They had business interests in Sicily, Cleveland, Miami, Cuba, Las Vegas, Reno and Hollywood. In New York, the Barzini family ran some of the gambling, sports betting, drug trafficking and prostitution. They were even rumored to have a toehold in Wall Street.
Barzini lures Sonny Corleone in a trap to kill him with the help of his shifty brother in law Carlo Rizzi at the Long Island parkway toll booth, Barzini hitmen shoot him more than 90 times with Tommy Guns, The trap was for Carlo to beat Sonny's sister Connie Corleone and get him to the Long Island Parkway. Sonny had already beaten Carlo to a pulp upon learning that Carlo was abusing Connie. Sonny's death does not go unavenged, however. Vito realises, during a meeting with the heads of the other crime families, that Barzini was responsible, and following Michael's ascension to power, Michael orders the deaths of the other Mafia dons to cement his position as the most powerful Mafia don in New York. Michael also has Clemenza kill Carlo after getting him to confess by falsely promising him exile instead of death for Connie's sake.
Corleone enforcer Al Neri, disguised as a police officer, shoots and kills Barzini, his bodyguard, and his driver on the steps of the New York Supreme Court courthouse at Foley Square, crippling the Barzini family.