Manuscripts in archives are primary source materialArchives USA indexes American Archives
National Archives has its own finding lists. Microfilm records can be borrowed on Inter-Library Loan.
Access to Primary Sources indexes microfilm collections of American manuscripts and government documents.
Digital National Security Archive picks up post-WWII international relations documents.
Declassified Documents covers Cold War era but includes miscellaneous documents outside large collections.
Additional resources are listed on From the Archives to Your Desk Top.
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