See the guide "Finding Primary Resources for Historical Research" for a more complete discussion of the library's resources.
Search the Randall Library catalog and WorldCat (see below for links) for history makers' names as authors. This should retrieve their memoirs, diaries and correspondence.
As you search subject topics in the catalog and WorldCat, note that the following subdivisions indicate primary source:
Early works to 1800
Notebooks, sketchbooks, etc.
Personal narratives (used in relation to specific events only)
Songs and music
Speeches, addresses, etc.*
*Used with individuals' names,classes of persons (e.g., soldiers), and organizations.
Early English Books: The library has a selection of early English books on microfilm. Each title is cataloged separately. There are also guides to the microfilm collection on the cabinets where the reels of film are stored.
Google Books: 12 million and counting!
Internet Archive: Another effort at making digitized texts freely available.