This is just a small sampling of useful digitized history resources. Keep looking. The collection you want is out there.
American Folklife Center Digital Collections
Arolson Archives: International Center on Nazi Persecution
The Avalon Project: Documents for Legal and Diplomatic History
Black Oral History Collection, Washington State University
California Digital Newspaper Collection
Calisphere, California History
Central Intelligence Agency (CIA)
Chronicling America Newspapers
Digital Public Library of America
Documenting the American South, University of North Carolina
The Harvard Project on the Soviet Social System
HathiTrust Digital Library
Hifumi En, Spokane’s Japanese American Community
Historic Washington State Newspapers
Hoover Institution Digital Collections
The Huntington Digital Library
Jimmy Carter
Library of Congress, Digital Collections
Louisiana History
Making of American Books, University of Michigan
National Archives, UK
Native Hawaiians/Kanaka Culture and History
Nines
South Asian American Digital Archive
Sub-Saharan African Digital Archives
The Vault, Federal Bureau of Investigation