Books published during the historical time period you are researching are primary sources. Search Google Books for digitized copies:
(click on image to enlarge)
Combining search words for your topic PLUS any of the the search words below:
This was found using a search for "slave narratives"
U.S. History in Context is a great database to find primary sources. You can limit to primary sources or search for just a specific kind of source. Use the information and the images in the example search below to guide you in your search.
(click on image to enlarge)
Notice once you've limited to primary sources and see the results, there is a way to further narrow, or at least look to see what types of sources are included in the results such as government document, speech, editorial, excerpt, interview...etc.
(click on image to enlarge)
Each guidebook provides suggestions for primary sources for different events in history.
Term Paper Resource Guide to African American History by 
Term Paper Resource Guide to American Indian History by 
Term Paper Resource Guide to Latino History by 
Term Paper Resource Guide to Colonial American History by 
Term Paper Resource Guide to Nineteenth-Century U. S. History by 
Term Paper Resource Guide to Nineteenth-Century World History by 
Term Paper Resource Guide to Twentieth-Century United States History by 
Term Paper Resource Guide to Twentieth-Century World History by 
Daily Life of African Americans in Primary Documents [2 Volumes] by
Suggestion: Click on Book Index (near top of the book's homepage) and, from there, click on link(s) to desired article(s).
American Civil War: Interpreting Conflict Through Primary Documents [2 Volumes] by
Suggestion: Click on Book Index (near top of the book's homepage) and, from there, click on link(s) to desired article(s).
Annals of America by 