If you live in the Midwest, there are two museums that you have to go to.
The Lincoln Presidential Library and Museum in Springfield, IL
The City Museum in Saint Louis, MO
The first one is self-explanatory. The second can be described as a giant 5 story scrapbook of art and architecture that you can touch, climb on and experience like no other museum I have ever been to. It is a great place for kids and adults to get some exercise. You have to check it out, especially if you have kids.