Georgia Farm Boy aka San Francisco Mabel Joy was written by Mickey Newbury, and was originally released by him in 1969.
I dont know when the Box Tops version was recorded, but it was included on the Sundazed reissue of The Letter/Neon Rainbow. This album was originally released in 1967, which obviously pre-dates Newbury's release by one year. Maybe this explains the alternate title? I'd love to find out.
Thanks to Bill Cunningham for use of the personal Box Tops photos.