"HathiTrust provides long-term preservation and access services to digitized content from a variety of sources... Items in the public domain are in full-view for everyone and items held in copyright are searchable."
Collection of public domain and copy-permitted historical texts for educational use. It includes not only documents associated with the "western civilization" approach to history but also provides much information on Ancient history, Byzantine, Islamic, Jewish, Indian, East Asian, and African history. You will also find many documents especially relevant to women's history and LGBT studies.
TOP Searching Tools to Find Information about Primary Sources/Archival Collections
"Includes over 5 million records describing archival materials, bringing together information about historical documents, personal papers, family histories, and more." ArchiveGrid is largely made up of records from WorldCat.
"Helps users discover biographical and historical information about persons, families, and organizations that created or are documented in historical resources (primary source documents) and their connections to one another. Users can locate archival collections and related resources held at cultural heritage institutions around the world."
Use terms that define your topic plus terms that define the type or primary source such as correspondence, letters, personal narratives, diaries, etc. Once you perform a search, you can also limit by "Resource Type" on the left side of the screen.