Primary sources are original literary texts and other materials produced during the time period being studied. These can include manuscripts, editions of books, newspaper articles, book reviews, and other materials produced during the time period that document events.
UIUC provides a number of resources for finding primary sources that will be useful to you.
The Library has a number of databases that contain primary source material for African-American literatures:
Uncle Tom's Cabin & American Culture-- a multimedia archive at the University of Virginia