According to the Native American tribes of the Kiowa and Lakota, some girls went out to play and were spotted by several giant bears, who began to chase them. I an effort to escape the bears, the girls climbed atop a rock, fell to their knees, and prayed to the Great Spirit to save them. Hearing their prayers, the Great Spirit made the rock rise from the ground towards the heavens so that the bears could not reach the girls. The bears, in an effort to climb the rock, left deep claw marks in the sides, which had become too steep to climb. (Those are the marks that appear today on the sides of Devil's Tower.) When the girls reached the sky, they were turned into the star constellation the Pleiades.
This is only one version of how Devil's Tower came to be.
