If you can, try to plan your visit to Des Moines to fall during the Iowa State Fair, which takes place every August. Even if you can't make it the State Fair, there is a Fair Tour that features occasionally fair-related events in the months leading up to it, and they are spread around the area. The fair itself has everything you could want. There is a parade, live concerts from top names, livestock and agriculture shows and concerts, rides, food, and more. Some things are free, but expect the headlining concerts to have an admission fee.
Address: 3000 E Grand Ave,
Des Moines, IA 50317