The following quote by N. Scott Momaday (The Way to Rainy Mountain, 1969) can be found in the visitor's center at Devil's Tower National Monument, WY. It answers the question: What makes the Tower significant?
"At the top of the ridge, I caught sight of Devil's Tower upthrust against the gray sky as if in the birth of time the core of the earth had broken through its crust and the motion of the world was begun. There are things in nature that engender an awful quiet in the heart of man; Devil's Tower is one of them."
A special thanks to the kind staff at the visitor's center for furnishing pencil and paper to record the quote.