After interviewing the grandson, I wrote
A third eyewitness to John Henry's contest with a steam drill and death near Dunnavant, Alabama, has turned up. His son is still living.
The other two are C. C. Spencer and an uncle of Glendora Cannon Cummings, both informants for Guy Johnson, ca 1927.
Now I have interviewed the son and the story is different. The son, who is now 86, says that his father did not witness John Henry's contest and death, but he had two friends (named) who did.
This evidence loses credibility somewhat by one further step of removal from the event: witnesses -> friend -> son. However, it gains an eyewitness, making four if we believe all accounts.
I got another useful bit, however, from the son. He told me that his father had said that John Henry had been brought from Mississippi. That makes the third witness to this effect, the first being C. C. Spencer (1927), the second Mrs. Davis (1955), and now this (2008).
An interesting development with C. C. Spencer is now under investigation. He appears in the 1920 census in Emery County, Utah, as a coal miner. His wife's name is Luceal.
It appears that he was in a card game on Saturday night, just before Christmas, 1922, in Mohrland, Emery County, Utah. It was a three-way game, and Spencer continously lost while another man continously won, the third man breaking even. This led to friction and Spencer wound up shooting and killing the winning gambler. There was a manhunt leading to his capture. He was convicted in 1923 and sentenced to life in prison, but in 1926 his sentence was commuted to five years. He applied for early release in 1927 and it appears that he may have received it.
A Charles C. Spencer appears in the 1930 census as a crane operator in a factory in Salt Lake City. He was married but not living with his wife.
A Charles Curtis Spencer, b. July 7, 1878, registered for the draft in 1918 in Henry County, Virginia. His wife's name is Lucinda P. Spencer.
A comparison of the signatures of Charles C. Spencer (Utah parole request) and Charles Curtis Spencer (draft registration) is inconclusive to my eyes. They look rather different (one is a thin line, the other bold; the bold one is crowded into a given space, the thin one is not crowded), but their underlying structure is similar. I need a handwriting expert, I think.
In any event, these developments add a bit of "color" to the John Henry story.