For the record, the US Army Military History Insitutue (USAMHI) / Army Historical Education Center (AHEC) at Carlisle Barracks, PA is the main US Army repository for documents and records. USAMHI is one of the top research facilities in the Army History Program, and as such, is an appropriate facility for donating any documents and records, personal or otherwise, dealing with any aspect of US Army History. If a person wishes for his or her donated materials to be available to the widest possible audience of future historians and researchers, USAMHI is the best place. Donations to other Army historical facilities such as that operated by the Engineers is fine too, but rest assured items donated to these facilities will not be available to as wide a specturm of historians and researchers as those housed at USAMHI. Thus, a person conducting serious research on Operation Nordwind will almost certainly go to USAMHI, but not the Engineer's repository. As a result, important material regarding the Engineers' contributions to defeating Operation Nordwind might be missed.
Hope this helps.
Jim