The documents are available in the original Spanish or, in English translation.
Here is Background on this key resource.
Look near the bottom of the page linked above for links to indexes and other tools for using this material.
American Indian History-Oral Interviews
American Indian Research Project at USD
Doris Duke American Indian Oral History Project, 1949-1972: Utah Indians
North American Indians
D’Arcy McNickle Center for American Indian and Indigenous Studies
Indian Claims Commission Materials (National Indian Law Library)
Indigenous Digital Archive (by NM’s Museum of Indian Arts & Culture)
Nation to Nation: Treaties Between the United States and American Indian Nations @ NMAI
National Museum of the American Indian
Protocols for Native American Archival Materials
Eugene C. Barker Texas History Collection [Briscoe Center for American History at UT]
PARES (Portal de Archivos Españoles) [Spanish-language access to Spanish archives on-line (including innumerable documents on the Americas)]