Robert Johnson wasn't the "start of it all". Many Blues artists were.
Willie Dixon (Zeppelin ripped him off excessively and were sued on a couple of occasions for it)
Howlin' Wolf (never gets mentioned in threads like this)
Albert King (ooh that fretboard drips of Delta blues)
Elmore James (one of the Best Slide guitarists of all time, if not the greatest. Sorry Duane but he was better and you were influenced by him)
Leadbelly is my fav. blues artist and was ripped off by many years later.
Personally, Robert Cray is one of the most underrated, rarely mentioned blues guitarists.