The Mobsters featured on Gambling-History.com all were affiliated somehow with gambling somewhere in the world and meet at least one of these criteria:
They were part of the Italian-American organized crime syndicate.
Examples: Al Capone, Santo Trafficante, Frank Costello, Vincent Alo, Lucky Luciano
They were allied Jewish-American racketeers.
Examples: Meyer Lansky, Benjamin Siegel, Mickey Cohen, Gus Greenbaum, Moe Dalitz
They were members of a band of criminals.
Examples: Purple Gang, Chesterfield Syndicate, Third Ward Gang, Barker-Karpis Gang, Waxey Gordon ring
They seemingly were lone operators, without obvious organizational affiliation, who acted thug like and committed crimes.
Examples: Benny Binion, Reggie and Ronnie Kray, Bernie Einstoss
They were known associates of the underworld but had the outward appearance of being clean, such as casino fronts.
Examples: Wilbur Clark, Allen Glick, Edward Levinson, John Drew