Robert Mitchum and Richard Widmark reportedly did not get along with Kirk Douglas because of his tendency to usurp control of the project from Director Andrew V. McLaglen.
Mitchum's speech in the Lakota language was shot right after his teacher read it to him just two times out loud! Mitchum only needed one take to do it flawlessly and his teacher said that it was the best Lakota accent he had ever heard.
Lola Albright (Rebecca "Becky" Evans) nearly drowned during the river crossing scene. The wagon she was in tipped over, and she was trapped underwater when the contents of the wagon fell on her and pinned her down. When they finally got her out, she was semi-conscious and spent the night in the hospital. A day later, she returned to the set, but they used a stuntwoman to re-film the river scene. In interviews, she said she was deeply traumatized by this near-death experience.
Though often described as making his film debut in Butch Cassidy and the Sundance Kid (1969), Sam Elliott appeared, while a college student, as an extra in this movie, filmed near his hometown in Oregon.