To search for books with primary sources, make sure to change the type of search to be a 'subject' search and include the word 'sources'; for example, 'women and sources' or 'china and history and sources'.
Personal diaries are also useful. You can find them by doing a subject search on 'diaries NOT fiction' (make sure the word NOT is capitalized).
Other subject terms to try:

Search over 100,000 books in the Library's Catalog and books from 127 Illinois college and university libraries in the I-Share Catalog.
Reference books (Call Number includes REF) do not circulate and must be used in the library.
Milestone Documents in American History: Exploring the Primary Sources That Shaped America
by
McCoy, Kelli, editor.
The American Women's Movement, 1945-2000
by
Nancy MacLean
Conversations with the Dead : The Grateful Dead Interview Book
by
David Gans
Terrorism: Essential Primary Sources
by
K. Lee Lerner and Brenda Wilmoth Lerner
War Letters: Extraordinary Correspondence from American Wars
by
Andrew Carroll