John Henry, a freed slave, happens across a railroad building project. An entire crew of freed slaves has been promised land if they can finish by deadline, but they're exhausted and unable to continue. John, though, has the strength of ten men, and revitalizes all of them. But despair sets in again when the railroad sends a steam hammer to replace the crew and burns the contract. John proposes a challenge: man against machine. After a heroic effort, including a tunnel through solid rock by swinging two hammers at once, John wins, but he also collapses in his wife Polly's arms. She's recounting this whole story to their young son, to explain why his father was so great.