Who was the man in the children's stories...?

Haha, John Henry is the person I think you are talking about. Here's a website about him: http://www.ibiblio.org/john_henry/

Folk hero, John Henry ("died with a hammer in his hand, Lord, Lord, he died with his hammer in his hand")

"Like other "Big Men" such as Paul Bunyan, Pecos Bill, and Iron John, John Henry also served as a mythical representation of a group within the melting pot of the 19th-century working class. In the most popular version of the story, Henry is not born into the world big and strong. He grows to become the greatest "steel-driver" in the mid-century push to erect the railroads across the mountains to the West. When the owner of the railroad buys a steam-powered hammer to do the work of his mostly black driving crew, to save his job and the jobs of his men, John Henry challenges the owner to a contest: himself alone versus the steam hammer. John Henry bests the machine, but exhausted, collapses and dies."

John Henry. He was a folk legend, but at least one writer believes he has identified the man behind the legend and has written a book. There's a good article at NPR with a link to a version of the song:

http://www.npr.org/programs/morning/features/patc/...

There have been several children's book versions of the story including one by Ezra Jack Keats:

http://www.amazon.com/John-Henry-Ezra-Jack-Keats/d...