I don't think Gaines gives the character Jefferson a last name in A Lesson Before Dying. His godmother is named Emma Glenn, but she is not a blood relative. I've read the book and several critical essays, but I cannot find a last name. Perhaps that was intentional. One of the things Grant uses as an argument against teaching Jefferson to read is that he has no relationship to Jefferson; he has no obligation to him. By not having a last name, perhaps Jefferson could be said to "belong" to everyone and is everyone's responsibility. Just a thought.
It didn't give a last name..
The author,Earnest J. Gaines, of "A Lesson Before Dying" did not give Jefferson a last name. He is named only as Jefferson and is one of the main characters that make up this amazing,intriguing novel.