Be sure to get a variety of types of sources as you research African American History. Use WorldCat to identify books that we own and books that we can get from other libraries via the IDS office. To find primary sources, use words like narratives, memoirs, collected papers of..., documentary history of...., source, etc. Be careful not to order items via interlibrary loan if they are only owned by a few libraries; we usually can't get those. Some publishers are giving Google Books the right to post the full text of books online, so try looking up specific books there once you have titles.
Look for scholarly articles written by historians using America: History & Life.
Use New York Times Article Archive to find out about articles from the 1950s, 60s, and 70s; you can get the articles themselves on microfilm. Use ProQuest Newspapers and Custom Newspapers to find past newspaper articles from major U.S. cities as well as national newspapers like the New York Times and USA Today, for the last 20 years or so. Google News Archive also has full text articles from selected newspapers, although probably just more recent ones. Newspaper Links has links to newspapers currently in publication. A look at the web page of a newspaper should uncover whether it was in publication during the time you are researching. You can then ask the IDS office to get the microfilm for you. Finally, use Alternative Press Index to get articles from non-mainstream publications.