I'm trying to go beyond my oldest set of African-American ancestors (May Jefferson b1820, and Eve Jefferson b1840) in South Carolina. I presume I have to take the search offline at this point, but I'm not sure what I should be looking for or where I should be looking for it. The oldest records I have to work with so far are:

1)an 1880 census for Orangeburg, SC where these ancestors appear. (For some reason I can't find any of my relatives in the 1870 census).

2)a death certificate for one of their sons who died in 1939. (The certificate does not list the mother's maiden name.)

Any advice on where to go next to find more information?
Thanks