I love Sammy Cahn's work, and he had an absolutely wonderful one-man (in a way...) show called Words & Music that he toured the country with, and I think it even played on Broadway. (The "in a way" part is that he had three singers to help out on certain numbers throughout the evening.) The one quibble I had with it is that whenever he came to another city, he would change the words from "Chicago" to wherever he was -- and tweak the words to fit that "town." I'd been waiting the whole show to hear "My Kind of Town (Chicago Is)" and it was such a letdown to hear it about Los Angeles. Ack.
No, it's about Chicago. That's like changing, "I Left My Heart in San Francisco" to "I Left My Heart in in Tallahassee" just because he playing there and trying to suck up to the audience. This not only is about Chicago, it has a context. And that context is that the gangster Robbo who's turned benevolent has just been found not guilty of trumped-up charges, left the courthouse and been greeted by an overjoyed crowd.
Which is when he sings this. (This video quality isn't great -- but the song is.)