We stopped off at the President Truman Library & Museum in Independence. Unfortunately for us, we arrived at 4:30 pm and it closes at 5 pm. We literally ran through the museum to try and take in as much as we could in that short amount of time. I would highly recommend this museum (and give yourself more time!).
Included in the museum was a replica of the Oval Office and President Truman's famous "The buck stops here" desk plaque; letters and mementos from US citizens (including a button down shirt with a letter from a congressman stating that a gentleman felt he was being taxed so much that he literally sent the "shirt off his back"!); and hand written notes written during the time he decided to use the atomic bomb (ironically we were at the museum on the anniversary week of the bombings). It had so many exhibits that I would have loved to read and look at more closely. Hopefully we will be back this way again.