In the beginning of the film, after the massacre of Wounded Knee, we see chief Big Foot lying dead in what seems to be an unnatural pose, left arm raised from the ground. This is an accurate depiction of the Miniconjou chief's actual death pose which was photographed.
The trivia item below may give away important plot points.
The characters of Viggo Mortensen (Frank T. Hopkins) in Hidalgo and of Tom Cruise (Nathan Algren) in the Last Samurai have very similar traumatizing backgrounds. They both suffer from PTSD from helping or aiding in the massacre of Native Americans, they lose themselves in alcohol and an work 1800's wild west type show, followed by receiving an offer to travel to a foreign land for a large amount of money, and are wholly changed by the experience.