Jim:

Extremely interesting. Since a long time ago, before the internet, I assumed that the song was based on a historical event. Apparently, this is not confirmed. Just came here from Wikipedia. Growing up we had physical encyclopedias in the house, and we had a set of books on the United States breaking it down state by state, directed at young people. I fancy the history/ legend of John Henry might have been in one of these.

I also know the Allan Sherman comedic version almost by heart. Also from my youth.

I haven't gone through the Mudcat threads on this song. Mudcatters with deep backgrounds have probably weighed in and are worth reviewing. If we don't have a date for the supposed contest, the song versions may provide geographical ranges and dates.

Your approach reminds me of another comparison between art and history and why we need to be careful in thinking we understand what something is about:
A frequently repeated television show to this day is MASH. If you ask most young people, seeing the show for the 'first' time in this day and age, and ask them what the show is about, they will most likely say: "Korea". If you ask someone of an age to have seen the program when it first aired, they will say: "Vietnam".

Good luck with your study and work.