The burnt-red badlands of Montana's Hell Creek are a vast graveyard of the Cretaceous dinosaurs that lived 68 million years ago. Those hills were, much later, also home to the Sioux, the Crows, and the Blackfeet, the first people to encounter the dinosaur fossils exposed by the elements. What did Native Americans make of these stone skeletons, and how did they explain the teeth and claws of gargantuan animals no one had seen alive? Did they speculate...