|--Diaries||--Songs and music|
|--Notebooks, sketchbooks, etc.||--Facsimiles|
|--Records and correspondence||--Manuscripts|
The history research guide and 20th century U.S. history guide contain some references to some of the largest digital archives online.
For help in working with primary sources, consult History Matters. For a good definition and review of primary sources, see this tutorial.
An effective research strategy is to consult the reference lists and bibliographies of books and journal articles that you find; these bibliographies should help you identify other valuable materials on your topic. Your next step is to determine whether KL owns that book or journal article.
e.g.: Suppose you find the following citation in the bibliography of a book or article you're reading:
Bernstein, B. J. "Truman and the a-bomb: Targeting noncombatants, using the bomb, and his defending the 'decision.'" Journal of Military History 62 no. 3 (1998): 547-570.
Check to see if KL owns this journal (Journal of Military History) by searching Kresge Library’s Library Catalog. (Be sure to perform a Journal Title search using the title of the journal — Journal of Military History — NOT the title of the article.) If Kresge Library does not have this article, you can order a copy through Interlibrary Loan.
KL has a video tutorial on how to find journals owned by the library
Refworks allows you to create a personal database of references and automatically generate formatted bibliographies for your projects.