If you haven't been to Chicago before, be sure to allow yourself a couple of days there either at the beginning or end of your trip. It's an awesome city with a lot of cool things to see. I was just there for the last stop on a road trip in July, and I absolutely fell in love with Chicago. Some activities I'd recommend:

The Chicago Architecture Foundation does a really great boat tour of the city along the Chicago River. You learn a lot about the history of the city and its many beautiful buildings. It was a really great way to see the city. The tour lasts 90 minutes, tickets are about $30, and the boat docks near Michigan Avenue & Wacker Drive. Well worth the time and money.

The Art Institute of Chicago, in Millennium Park, is a fantastic museum. Admission is $18 (free if you're a teacher), and the collection includes all kinds of great pieces (for example, American Gothic, Picasso's Old Guitarist, and Hopper's Nighthawks). Plus, Millennium Park is a must-see spot with great sculptures throughout and a really beautiful music pavilion.

Wrigley Field is obviously an American icon, and the Cubs are in town at the start of your trip (playing the Giants, then the Cardinals). We didn't catch a game during our visit (the Cubs were on the road), but my baseball-loving boyfriend did insist on a pilgrimage to the field anyway.

For an awesome view of the city from 96 stories up, have a drink at the Signature Lounge in the John Hancock Building. The view is spectacular.