Sorry I haven't responded sooner. I've been working on my Rigsby notes and suddenly realized I hadn't checked here lately.
I think I have the Cannon and DeKalb Rigsbys figured out up to 1880, but there's one branch I can't place. I still haven't checked the 1900 census, though, so I don't know where your William fits in. Let me know when you find out who his father was.