It’s pretty hard to find smoked BBQ in Chicago though I will vouch for Merle’s smoking their own meat. They also do some nice dishes that are a little more Tex-Mex style and a great dish called "double shot pork chops" that are grilled with a honey and whiskey glaze.
While much "chicago-style" BBQ may not appeal to purists. I believe there is something to be said for well cooked ribs that have never been within miles of smoking wood. Gale Street Inn and Biassetti’s are both great.