The immigrant groups that have historically gotten the most attention in Chicago are the Italians and the Irish. Italians because of Al Capone, and the Irish because, well, they’re everywhere there. This is not to take anything away from Chicago-Irish notables like Mrs. O’Leary (whose cow supposedly started the Chicago fire) and bartender Mickey Finn, who was so notorious for drugging and robbing his customers, he became the basis for the idiom “slip a Mickey.”
Central Europeans don’t get much credit for making Chicago what it is, but if you added up all the Poles, Czech and Slovaks the city contains they’d outnumber pretty much everybody (Chicago has more Poles than any city in Poland save for Warsaw). For all that they’re all but invisible to most people, except perhaps at a pop culture level. For it’s the Central Europeans who have come to define the “typical Chicagoan.” They’re the ones who contributed, on top of the thick base of New York-ese brought to Chicago by transplanted workers, the nasal tones and staccato delivery that makes the Chicago accent distinctive. Don’t get me started on the push broom mustaches.