Amos Easton: Dude, I'll take it. You're a rock star, Starship. Thanks for finding that.

I've been reading biographies of bluesman lately, and have found that most of the big names "wrote" songs that were "based on" older songs by other artists. e.g. Howlin' Wolf's biography said that his song "Crying at Daybreak" was based on Charley Patton's song "Crying at Daybreak". The Wolf got a ton of stuff from Patton.

I think the answer is that almost all blues were written by Mr. Traditional or Mr. Public-Domain. :)