Timothy "Big Tim" Sullivan, long time political boss of Tammany Hall, is committed to a sanitarium.
The Kim Lan Wui Saw Tong is established in New York's Chinatown, eventually declaring war against the On Leong and Hip Sings later that year.
Joseph DiGiovanni, a Black Hand leader, begins operating in Kansas City. With his brother Peter DiGiovanni they would later control bootlegging in Kansas City during Prohibition.
Mock Duck is convicted of running a policy game and sentenced to imprisonment at Sing Sing Prison.
July 15 - Members of the Lenox Avenue Gang including leader Harry Horowitz, known as Gyp the Blood, and top lieutenants Jacob Seidenscher, Louis Rosenberg, and Francesco Cirofici kill prominent New York gambler and police informant Herman "Beansie" Rosenthal. They are later convicted of Rosenthal's murder and executed the same year.
September - Republican State's Attorney John E.W. Wayman, shortly before his term of office is to expire, officially closes down Chicago's South Side "Levee District". The long-time vice district had been a hotbed of criminal activity for Chicago's underworld, as well as a major source of political power for Chicago's First Ward Alderman such as Michael "Hinky Dink" Kenna and "Bathhouse" John Coughlin, since the 1890s.
October 16 - Frank Costello is again arrested for assault and robbery and is later released.
November 6 - Owney Madden is shot by several thugs while at a 52nd Street dance in New York.
William Daddano Sr. (William Russo), Chicago crime syndicate enforcer.
March 19 - Nicholas Civella, Kansas City crime syndicate leader.
August 1 - John Ormento "Big John", Lucchese crime family Caporegime, labor racketeer and drug trafficker.
September 18 - John Scalish, Cleveland crime syndicate leader and National Crime Syndicate labor racketeer.
November 7 - David Miller (David Yaras), Chicago gambling racketeer.
July 15 - Herman "Beansie" Rosenthal, New York gambler and police informant
October 5 - Jack Zelig, Eastman Gang leader