http://www.architecture.org/tours
http://shorelinesightseeing.com/
There are more than 85 architecture tours available in Chicago. We were told that one of the things that we must do was take the architecture tour by boat. We didn't have any objections to that, but in terms of trying to figure out which one to take or to book in advance, we were not having any luck. Eventually we just went to Navy Pier, saw people at booths, and the one we took happened to cost the special price of $18.71 per person, because it was the anniversary of the Great Chicago Fire that happened in 1871. (That was a two-day special, because the fire lasted over two days.)
We loved our tour. We saw a lot, the guides had great information, and it is definitely worth seeing. That may have been the result of dumb luck, but there didn't actually seem to be a lot of competition. It may be that there are different routes for different types of year, or times of day, but the main difference seems to be your mode of transportation.
I had questioned whether you could really see that much by boat, but I was amazed. Portland has a river running through it, but the way it works is almost like you have two separate cities connected through 10 bridges. The Chicago River does not seem to disrupt Chicago. I guess it is narrower, and it has 45 bridges, and you are always crossing it without it being a big deal. By boat we were able to see an amazing number of buildings, and we also got to go past the spot where they dye the river green.
I had known that Chicago was important in architecture. I sort of knew that already, but I had made a point of reading Erik Larson's
The Devil in the White City before the trip, and so knew some of how the 1893 World's Fair was constructed and how it influenced others, and also a little about Chicago's importance to the development of the skyscraper and even a little about Frank Lloyd Wright.
On the tour, our guide made another point, which was that after the fire they had to do a lot of rebuilding, and so they could make conscious decisions about how things would look and be laid out. Most cities go through different phases in development, but Chicago got a reset.
Still, all of that is thinking about decades past and they also did a great job of pointing out more recent developments, and their influences and the stories behind why some buildings ended up the way they did.
Also, there were things that went beyond architecture, like an unusually large post office, which was necessary because you have three large mail order businesses, with Mongomery Ward, Sears, and Marshall Field. Then, you need an even bigger building, but in the meantime you have constructed something that they can use for Gotham, and she could tell us about seeing the Batmobile driving around when they were filming
The Dark Knight.
So I highly recommend taking an architecture tour on the Chicago River, and I don't think you need to stress about it. Just show up and take one, and it will work out. That's how it happened for us.