Sorry, I' haven't done research back to Africa. I trace descendents in this country. There are African American genealogical societies. The natl Park Service on its website has an alphabetical index of more than 200,000 black solders who served in the Civil War. My grandfather worked in the Western Pennsylvania coal mines.
Research begins in county records where they settled.
Census records are held for 72 years to protect privacy. I don't know what month. Also, civil registration of birth, marriage and death on a nationwide basis began in Ireland in 1864. I have found three sisters that I had lost touch with since my birth. It is possible.