Dylan Haters Rejoice!

PLB and some royalty shall be glad to know that I'm now reading Bob Dylan's memoir Chronicles. The book is very interesting as he recounts the days before he recorded and when he was famous and living in Woodstock. Only problem I have had with his writing is that he uses a very random stream of conscious style (like blogging). But I should've known that his book was off to a good start when he name drops Jack Dempsey. Now can you tell me who Dempsey was?