"It is impossible to come to the conclusion that the song character's name was Margaret without using as one of the premises that the real John Henry had a wife named Margaret. So it could never prove anything." - Nerd
Henry Dabney, of Copiah County, Mississippi, had a wife named Margaret, as is shown by both marriage and census records. According to the census, he was born 1850-51. He is a *candidate* for the historical John Henry, so finding a plausible series of mutations from Margaret Dabney to Polly Ann carries some logical force supporting this his candidacy. Names that are logical intermediate stages ("Maggadee," "Mary Magdalene," and "Mary Ann") are in the record, that is, they have been recovered in tradition.
Henry Dabney is also a candidate for the slave boy "Henry" mentioned by Letitia Dabney in her memoirs. During the Civil War, this slave boy was a teenager, which fits the census records for Copiah County Henry Dabney at least roughly.
The logic does not lead to the "conclusion" that the historic John Henry's wife was named "Margaret," nor does it "prove anything." If you want proof, you need direct documentation, which no one has for any candidate for the historic John Henry.
Absent such documentation, one must deal with testimony, any particular "fact" of which is likely (but not necessarily) untrue, and indirect documentation. What I've been doing is testing the testimony of several informants who placed the historic John Henry at Dunnavant, AL, in the 1880s. The testimony of C. C. Spencer is particularly rich in detail, some clearly erroneous, but much backed up by documentation that I've turned up. The documentation does not concern John Henry himself but rather Spencer's story about John Henry (that he was from Mississippi, that his "captain" was a man named "Dabner" ("Dabney"), that he worked on "Cruzee" ("Coosa") Tunnel, etc.)
My claim is not to have "concluded" or "proved" anything except that the Alabama scenario is much better supported by testimony and documentation than the West Virginia scenario. Indeed, there is so much consistent circumstantial evidence for the Alabama scenario that I think it likely to be correct.
If you think Scott Peterson was wrongly convicted because the evidence was entirely circumstantial, then you will certainly have problems with my arguments.
Anyhow, I haven't yet given up on finding direct documentation. I want to see that grave marker with "Here lies a steel driving man" on it.
When and if it is found, I'll definitely let you know.