by Geoff O’Keeffe To the east lie the Black Hills, to the west, the Bighorn Mountains. Between is a vast prairie: grasslands, sagebrush, lightly forested in places, sometimes lush, most often bone dry. The rivers are iconic, the stuff of legends: Yellowstone, Powder, North Platte, Bighorn. On this side of the Divide, all rivers flow eastward, joining the Missouri and eventually the Mississippi, heading toward the Gulf of Mexico. This is enormous land. Barely imaginable. This and so much more was Red Cloudâ€™s land. From the Dakotas to Idaho, Montana to Nebraska,......