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U.S. Attorney Thomas Dewey successfully prosecutes mobster Jacob "Gurrah" Shapiro for violating the Sherman Anti-Trust Act. Shapiro receives a two-year sentence.
Syndicate numbers runner and bookie Lester "Binny" Binion is forced to flee Dallas, Texas. Binion eventually opens Binion's Hotel and Casino in Las Vegas, Nevada.
May 1 – Alvin "Creepy Karpis" Karpowicz is arrested in New Orleans, he is the last of the public enemies to be captured and is the only public enemy to be captured alive.
May 19 – , the sister of Buffalo, New York mobster , is killed by a bomb explosion in an attempt on Maggadino's life.
June 6 – As part of his crusade against organized crime, U.S Attorney Thomas Dewey prosecutes New York mob leader Charles "Lucky" Luciano for pandering. On this day, Luciano is convicted. He would later be sent to the Clinton Correctional Facility in Dannemora, New York.
July 15 – President Franklin Roosevelt orders the arrest of Ignazio "the Wolf" Lupo for violating the terms of his parole to serve the remaining sentence stemming from a counterfeiting charge in 1918.
August – While again attempting to return to Manhattan, Ciro Terranova is arrested on a second vagrancy charge and is held in custody.
August 17 – "Big Nose" , leader of the Philadelphia crime family, is gunned down by the rival Lanzetti Brothers. This would begin a five-year gang war lasting until the death of William Lanzetti in 1939. After Avena's death, underboss Joe Bruno assumes control of the Philadelphia organization from his headquarters in New Jersey.
September 12–13 – Joseph Rosen, a Brownsville, Brooklyn candy store owner and government witness against Louis "Lepke" Buchalter, is murdered by Emmanuel Weiss, and Harry Strauss. The crime would remain unsolved until 1940, when mobster Abe Reles became a government informant and implicated Buchalter.
