This site includes archived material in special collections across the United States. Many of these items are not items that will be returned on a Google search. Results will link users to the specific institution holding the material where more information about availability, use, and copy acquisition can be obtained.
From their site:
ArchiveGrid includes over 5 million records describing archival materials, bringing together information about historical documents, personal papers, family histories, and more. With over 1,000 different archival institutions represented ArchiveGrid helps researchers looking for primary source materials held in archives, libraries, museums and historical societies.
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