A good source of information are contracts made between former plantation owners and the newly freed men and women. They show former slaves assuming surnames for the first time, or revealing surnames that they had but were not allowed to use. Not all former slaves took the last names of former slave owners. They sometimes chose other surnames. You can also search for a plantation owner’s name in order to locate records for your geographical area. This new availability will be a boon to genealogists and historians.
Tombstones, not for everyone
Many genealogists spend a lot of time looking for marked graves. But many people could not get a permanent marker because stone, such as marble or granite, was not available at that time or was too expensive. I know one prominent Georgia family in the late 1790s had to order a tombstone from New York City to be shipped to Georgia. So many graves, especially in rural areas, were marked in ways that did not survive. There are books for most Georgia counties that have listings of all the marked graves discovered in that county. The best collection is at the Georgia Archives.