Gregory Peck was a close friend of Jane Fonda and frequently attended political rallies with her. This film was the only movie that they appeared in together.
Burt Lancaster sued the production company after he was removed from the role of Ambrose Bierce due to his heart problems.
According to the American Humane Association, the scene involving the shooting of Gen. Arroyo's horse had no humane representative present but the AHA spoke with Gregory Peck, who was present during the entire filming of the scene. Peck described in great detail how the shocking effect was achieved, and assured the AHA that the horse, Twister, was not harmed. The AHA went to the California ranch where Twister is kept so that they could observe him re-create his specialty fall. He did, and they determined that he was in excellent health.
Luis Valdez, who helmed La Bamba (1987), was originally set to to direct, with Peter O'Toole as Bierce.
The lines Bierce quotes by the fire before the "skeletons" scene are the last lines of his famous short story "An Occurrence at Owl Creek Bridge".