According to American folklore, who dug out the Grand Canyon?
And the answer: Paul Bunyan.

In American and Canadian folklore, Paul Bunyan is a giant lumberjack and folk hero. Often accompanied by Babe the Blue Ox, Bunyan's character originated in the oral tradition of North American loggers, and went on to be publicized by author William B. Laughead.
As a story circulated for several decades before written recollection, it’s difficult to pinpoint exactly where and how Paul Bunyan came to be. At the height of Paul Bunyan’s circulation, the fabled "stories" known today were presented in short fragments in the lumber camp bunkhouses, often with different origins and details. The first known reference of Paul Bunyan in print appeared in the March 17, 1893 issue of Gladwin County Record. Under the local news section for the area of Beaverton it reads, "Paul Bunion is getting ready while the water is high to take his drive out."
It wasn’t until 1916 that W.B. Laughead consolidated the stories to create the folkloric image of Bunyan we know today. A series of pamphlets, released between 1914–44, were used to publicize the products of the Red River Lumber Company. These influenced other authors such as Esther Shephard, who wrote of the mythic hero in Paul Bunyan (1924). James Stevens, also a lumber publicist, mixed tradition and invention in his version of the story, Paul Bunyan (1925). These books restyled Paul’s image for a wide popular audience, as their humor centered on Paul’s giganticness rather than on knowledge of lumbering techniques.
Paul Bunyan remains an American folk hero even today. Listen to Disney tell Bunyan's classic tale below.
