For historical research, the phrase "primary sources" refers to items that were created at the time an event occurred usually by direct observers or participants. Primary sources are not limited to traditional text-based documents such as newspaper articles and journal entries; photographs, posters, audio recordings, video clips, books, and more can all serve as primary sources if they are used as evidence of the time in which they were created. It's not about the source type...it's about how the source is used for your research.
Other Notable Digital Collections
Annual Reports of the Commissioner of Indian Affairs
Annual Reports of the Bureau of American Ethnology
Other Government Reports and Publications