Re The original question. W C Handy seems to have had a lot to do with it.

There is an interesting thesis by Vic Hobson on line. https://core.ac.uk/display/2780531
I believe there is also a book by Hobson, and I would recommend his work.

Hobson goes over ground covered in some posts here eg Odum, Scarborough etc.

Hobson says: “W. C. Handy’s autobiography The Father of the Blues does not argue convincingly for a belief that the Mississippi Delta is the birthplace of the blues; there are far too many internal contradictions for that.”

and

“It is not that Handy convincingly argues for the Delta being where he first heard the blues; it is rather that later generations of blues writers have chosen to privilege Handy’s Mississippi recollections over his other statements.”

Hobson points out that Handy gave contradictory accounts of where he first heard the blues. What these accounts seem to have in common is a desire on the part of Handy to give the impression that his own ‘blues’ had what we might call a ‘folk’ origin.

Hobson also argues that Handy’s own use of the 12-bar was significant in that form coming to be seen as ‘the blues’.

At one time Handy claims to have been influenced by a three-line stanza piece ‘Got no more home than a dog, Lawd’, that he heard in 1893, and at another time by the famous Tutwiler incident which was years later.   The 1893 song was sung by a minstrelsy band, led by Phil Jones in Evansville. Hobson suggests that both accounts cannot be true.

It would take too long to sum up Hobson’s arguments. But if you are interested, it is a fascinating read. He isn't the only person to have looked into Handy's assertions and question how far the fit known facts and indeed eachother, but I can't lay my hands on these just now.

The Delta was cleared and drained surprisingly late. Something I read suggested that the blues was appearing before people moved into the Delta. So I think I agree that it is a myth, though it is a nice one.

Some posts have discussed the origins of phrase ‘the blues’ to describe a melancholy state of mind, this was current in England and examples from the 18th and 19th century are given in the dictionary.
A song about ‘having the blues’ was published in the USA mid-19th century. It was by Blesser and Graham.

The first piece to call itself a blues was published in 1909 and was called ‘The Alabama Blues’.

The first published piece to have a 12-bar section in was written by an Sicilian-American anarchist called de Maggio and came out in 1908.
Obviously the relationship between published blues, which would have been played via vaudeville and so on, and what people did in their homes and communities is another question. But I don’t think you can overlook the evidence of what was printed, as the ideas had to come from somewhere.

Some African American journalists were complaining about blues music on the vaudeville circuits as early as 1912.

A few snippets. Hope these are of interest. Abbot and Seroff have written a lot of interesting pieces about early blues and vaudeville.