Al Capone is the guy that everyone thinks of whenever the term "mobster" is thrown around. Throughout the 1920's Capone ran The Chicago Outfit, a criminal organization that specialized in bootlegging liquor (liquor being illegal during this time period), smuggling and prostitution. It was estimated that in 1925 his organization brought in over $100 million in revenue.
Capone was known for his extravagant lifestyle, often flaunting his ill-gotten gains with fancy clothes and cars. Capone served five years in Alcatraz for tax evasion, after which his health started to severely decline due to complications from late-stage syphilis, eventually leading to his death in 1947.