Since I was born in Illinois, and have some memories of certain areas, we decided to visit Springfield, IL and stay in Lincoln, IL, just to see the sights.
Springfield is a small city full of history, and a really great place to visit -- not too big to get around, and yet packed with things to do.
We had the opportunity to visit Frank Lloyd Wright's Dana-Thomas House. This is one of his Prairie Homes, and it is absolutely fabulous.
That said, you are not allowed to take pictures of the inside of the house, so these are from one of the informational sites I googled.
You simply can not get your mind around it, even when you are physically in it. It is breathtaking!
I visited with my grandma when I was about 10 years old, and I never forgot it. My kids won't forget it either.