Well, I am not a blues authority by any stretch of the imagination but I am a staunch proponent for the blues starting right here at Dockery Plantation and the surrounding area. I live in the heart of the delta, Cleveland, MS, and worked for a while with the Delta Center for Culture and Learning which is largely focused on blues education. Here's what I can attest to:

W.B Handy first heard the blues on the courthouse steps here in Cleveland which is now marked by a marker "The Enlightenment of W.B. Handy" at http://msbluestrail.org/blues-trail-markers/the-enlightenment-of-w-c-handy

The marker is a part of an extensive amount of research which created the The Blues Trail in the delta which runs, as Joe Offer mentioned, from Memphis all the way to the Vicksburg. The research was conducted by literally hundreds of true authorities who have scoured letters, diaries, calendars, and all manner of authentic sources of information.

By the way, I wish this thread had been seen earlier because I would have invited all of you the International Blues Conference which began today, of all days. We'd love to have you. Come on down and see for yourself. The "proof" is all over this place and we don't find showing you the sites. http://www.internationaldeltabluesproject.com/conference/

P.S. Just north of here is Hopson Plantation which is home to the Shack-Up Inn. I wonder if the Hopson mentioned in the first post is any relation....