George Stevens was originally slated to direct but bowed out because of script problems. His replacement, Robert Mulligan, had directed Gregory Peck to an Oscar in To Kill a Mockingbird (1962).
In The Big Country (1958)--starring and produced by Gregory Peck -the foreman (played by Charlton Heston) Steve Leech rides a very striking and beautiful black and white paint horse. Ten years later in this film--also starring Peck--the same horse is ridden by the Apache chief Salvaje (played by Nathaniel Narcisco).
After Patricia Neal recovered from her stroke, she had a choice of either this film or The Subject Was Roses (1968) as her comeback vehicle. Although she opted for the latter, she said she would like to have done this film also.
Although this was Gregory Peck's only film in 1968, he should also have been appearing in the Mirisch production "The Bells of Hell Go Ting a Ling a Ling." Scripted by Roald Dahl, this production was shut down after just six weeks shooting due to "poor weather conditions", a popular euphemism for a troubled shoot.
This was the final collaboration of producer Alan J. Pakula and director Robert Mulligan; Pakula left the partnership to direct his own films.