1. Archive.org
2. Library of Congress Digital Collections
3. National Archives and Records Administration (NARA)
4. Google Books
5. Project Gutenberg
6. Digital Public Library of America (DPLA)
7. Europeana Digital Library
8. The British Library Digital Collections
9. Smithsonian Institution Digital Collections
10. Internet Archive Book Images
11. HathiTrust Digital Library
12. The New York Public Library Digital Collections
13. World Digital Library
14. Europeana Newspapers
15. Chronicling America: Historic American Newspapers