History buff should definately take a sidetrip off I-81 to tour the homesites connected with Andrew Johnson, the seventeenth president of the U.S. Johnson is often remembered as the only president (except Clinton) to face impeachment hearings. Johnson faced this because he refused to give into Congressional pressure to change his cabinet. Doing so would have destroyed the checks and balances mandated by our constitution. In 1920, the Supreme Court ruled that the legislation that lead to the impeachment hearings was unconstitutional.
The historic site includes his original tailor shop located inside the visitor's center. The center also houses a small museum featuring books and other materials related to Johnson and the civil war. After that, you'll tour the Johnson home. It's fairly well preserved. The furniture is authentic. Children will be interested in seeing the toys owned by Johnson's grandchildren. The kitchen is also available for viewing and makes everyone appreciate modern kitchens. After visiting the home, make sure you go to the gravesite. It's at at the top of a hill and it's very dramatic. Johnson is buried wrapped in a flag with a copy of the constitution as his pillow. Perhaps one day he will be recognized as the true champion of the constitution that he was.
This is ran by the national park service, so it's pretty cheap. I think it's just $2 a person.