Between 1936 and 1938, the Federal Writers' Project of the Works Progress Administration interviewed over 2000 people who had been born into slavery. The result was dubbed the Slave Narratives Collection. While the interviews are not without their flaws, they are an essential primary source regarding human chattel slavery in the United States.
Indeed, the Narratives are the largest such collection of slave interviews from any slaveholding society.
The very worthwhile introduction to the Narratives can be read here.
They are organized by the interviewee's state of residence and can be read at this link.