The Barzini family was founded by Giuseppe Mariposa in the 1920s and replaced by Emilio Barzini in 1934, who expanded his territories beyond Brooklyn to include areas of Manhattan and Queens, while completely controlling Staten Island. The family 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 into an ambush with help from Sonny's shifty brother-in-law, Carlo Rizzi. Sonny is racing to his sister, Connie's apartment after Carlo, Connie's husband has beaten her. Sonny had previously beaten Carlo for his abusing Connie. Sonny has to stop at the Long Island Parkway toll booth where Barzini hitmen are hiding and shoot him more than 90 times with Tommy Guns. Carlo had staged the fight with Connie solely to get Sonny to the toll booth. Sonny's death does not go unavenged. During a meeting with the heads of the other New York crime families, Vito Corleone realizes that Barzini was responsible for the murder. 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. Pete Clemenza executes Carlo after Michael gets his confession for his part in Sonny's death.
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.