Except for newsletters, I don't think you are encouraged to send material directly to the library. Back when I was collecting stuff, the official procedure was to send material to the District Historian. He cataloged it and with assistance of the National Historian made a decision to send the material to the Nat Archives or somewhere else.
They are trying to avoid having multiple copies of the same stuff at the National Archives.
A word of caution - I was told that if you send something to the District Historian for cataloging you cannot get it back. Once they have it in their possession it is their's. So make sure anything you send them you or someone else you know doesn't need it.
