I suspect that:
John Henry, b 1847-63, was a slave owned by Thomas Dabney at Burleigh Plantation, Dry Grove, MS. Thomas' nephew, Frederick Yeamans Dabney, b 1834-35, studied engineering at Rensallear and went into the railroad construction business before the Civil War. At the end of the war, he left the Confederate Army as a Captain, settled in Crystal Springs, MS (12 mi sse of Dry Grove), where he was universally called "Captain Dabney," and resumed his railroad construction business. John Henry took the name of his owner's family, Dabney, and joined Captain Dabney's crew as a laborer. At some point he learned steel driving.
In early 1887 (or possibly late 1886), John Henry joined Captain Dabney in the construction of the Columbus and Western RR, from Goodwater, AL, to Birmingham. It was tunneled through Oak and Coosa Mountains, just south of Leeds, AL. Captain Dabney was Chief Engineer for the C & W. John Henry worked on the construction of the tunnels as a steel driver.
In mid-1887 the Coosa Tunnel ran into problems. They hit a peculiar hard granite layer that was very difficult to drill. On this account, the opening of the C & W would be delayed for months.
Captain Dabney considered the use of a steam drill. An agent from New York came down to pitch his machine. When Captain Dabney said that he had a man who could beat the steam drill, the agent offered a one-sided bet. He was very confident that this could not be, and he was also anxious to demonstrate his machine and make a sale. He offered to give Captain Dabney the steam drill if Dabney's man could beat it.
Arrangements were made over the course of a few weeks. On Tuesday, September 20, 1887, a hot muggy day with threatening rain, the contestants met outside the east portal of Oak Mountain Tunnel for their all-day match. At the end of the day, John Henry collapsed in a dead faint. He was revived by water thrown on him, but he was blind and he thought he was dying. He called for his wife, who was summoned and came. "Have I beat that old steam drill?" he asked, as his wife cradled the dying man's head.
Indeed he had. He had made 27 1/2', the steam drill 21'. The agent lost his steam drill and Captain Dabney lost John Henry, his best steel driver ("Champion of the world," one contemporary said). The steam drill was put to work on Coosa Mountain Tunnel, but it was nonetheless delayed by 6 months. The line finally opened on July 1, 1888.
John Henry's wife, who had cooked for some of the men in the railroad camp, stayed with some of the crew in that capacity when they went to West Virginia to work on the Elkhorn Tunnel, which was also completed in 1888.