There is a second location for the Library of Congress in Culpeper, Virginia. It houses the Packard Campus for media conservation – http://www.loc.gov/avconservation/
A childhood friend of mine is one of the archivists and he is involved in preserving silent films. Did you know that a majority of all of the silent film script writers and directors were women? There is additional information at this film describing the films and work of the National Film Registry:
Here is the link to a trailer for the documentary: https://www.youtube.com/watch?v=ea2tcWC2k0c
Here is a link to the full documentary: https://www.youtube.com/watch?v=yVF4BKISrI8
Well worth your time to view and learn about the great work of film preservation.