I’m a bit hazy about the history of the Mob/Mafia in Chicago. I believe Al Capone was busted around 1930 or so (income tax evasion), and was sent to prison for a long term. Who succeeded him as mob boss of Chicago? The Irish-American gangsters were pretty much finished (Dion O’Banion was killed by Capone’smen), and the Jewish mobsters were beaten out as well.
Whats the history from Capone on into modern times? Is the Mafia pretty much dead in Chicago these days? 
Capone wasn’t in the mafia. He was simply an Italian gangster, and while he was affiliated with the mafia, he couldn’t belong since he wasn’t Sicilian.
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Who succeeded him as mob boss of Chicago?[?QUOTE]
As Wumpus’s link indicates, the usual assumption is that Frank Nitti took over. Though it’s worth noting that Nitti died (by his own hand) before Capone did.
As a foreign outsider who’s lived just off Taylor Street, my understanding is that there’s still some sort of residual “organisation”, call it what you will, in place amongst some of the residents of Little Italy. But it’s a very, very pale shadow of its former self, by any measure.