Mark Rydell originally sought George C. Scott for the role of Wil Andersen because he despised John Wayne's views on the Vietnam War and other aspects of U.S. foreign policy. Ironically, some critics in 1972 believed that the way in which Wayne's character drafts the children out of school was a pro-war allegory for Vietnam.
The film takes place in late 1876. This can be observed in that: First, Wil Andersen notes that his older son would be nearly 40, and the tombstones of his sons Matthew and Lucius indicate their births in 1836 and 1837; and second, that upon later finding a skeleton with a spear in it, Andersen points out to one of the boys the nearby site of the Battle of Little Big Horn, which occurred in late June 1876.
Roscoe Lee Browne later said, "Some critics complained that I spoke too well to be believable. When a critic makes that remark, I think, if I had said, 'Yassuh, boss' to John Wayne, then the critic would have taken a shine to me."
As Wil Anderson is berating one of the boys for not yelling loudly enough while Slim is drowning, he says "Tryin' don't get it done." This echos John Waynes line, "Tryin' don't get it done, Dude" to Dean Martin's character in Rio Bravo (1959).
Shortly before filming began John Wayne gave an interview with "Playboy" magazine in May 1971 which caused controversy over his views on the civil rights movement, the treatment of Native American Indians, and gay rights.
When Mr. Nightlinger (Roscoe Lee Brown) first meets John Wayne's character Mr. Anderson and is asked about his experience in cattle drives....he mentions the Oregon trail, Chisum and Sante Fe. John Wayne played John Chisum in the film "Chisum" previously in 1970.
The trivia items below may give away important plot points.
When John Wayne informed Bruce Dern that Dern's character would shoot Wayne's, he told Dern that audiences would hate him for it. Dern responded by saying, "Yeah, but they'll sure love me in Berkeley."
Charles Tyner, who played the stonemason that carved Wil Anderson's gravestone, played another stonemason specializing in memorials four years later in Family Plot (1976). That film also starred Bruce Dern (this time as the protagonist) and also featured a score by John Williams.