a couple of weeks ago we (brother, dad & i) happened to be driving past our local library and saw a trailer in the parking lot with library of congress on it. interest piqued we stopped to look. just my brother & i went check it out. it turned out to be the library's rolling exhibition.
it gives an overview of when the LoC was started & what kind of things they have there. it was really interesting, IMHO, and it made me want to go see the real thing even more.

here's the schedule of stops.