On June 25, 1876, a village of some five thousand Lakotas and Cheyennes camped on the Greasy Grass River (today’s Little Big Horn) was famously attacked by George Armstrong Custer and his vaunted Seventh Cavalry. The Indians were followers of the powerful Húnkpapa holy man Sitting Bull, and, like their leader, most of them wanted nothing to do with white men. They simply wanted to be left alone, to live separate from the Euro-Americans who’d been steadily encroaching and trespassing upon Lakota lands for decades. With shouts of “Hóka hé!” (Come on!) and “The Earth is all that lasts!” the...