Recently I went on a River North architecture tour in Chicago. The tour was sponsored by the Chicago Architecture Foundation and cost $15 / each for non-members, which was money well spent. Here is a link to the tour.
The tour started near St. James cathedral at Rush and Huron (upper right, photo). This church was constructed right before the Great Chicago Fire of 1871. The center, middle photo shows the tower on the right that survived the fire; you can see the damage to the stones. On the lower left you can see the Episcopal center for the St. James cathedral built in a modernist style; this was almost torn down during the great real estate boom but it survived and now is probably safe for a few years since construction has come to a standstill. Driehaus Capital Management helped greatly with the neighborhood, and the top photo shows their headquarters. The bottom center photo is a classic car in their courtyard and the Driehaus museum features a prominent building from an early baron with immense stone walls in an attempt to make it fireproof.
Friedman Properties, owns a vast number of buildings in the neighborhood and was instrumental in building it up. I recommend going to the company web site where they have a company newsletter on all the changes in the area and an interview with the founder. Other buildings of note include one with odd green stone, the Dana Hotel (on the lower left) with the modernist front and exposed concrete back (note the "diving board" on the top, too); that cool triangular building in the lower middle, and the Excalibur nightclub which used to house the historical society on the lower left (the first one burned down, so they tried to make it fireproof).
Cross posted at Chicago Boyz