The sequence with Powell riding a horse in the distance was actually a dwarf on a pony. It was filmed in false perspective.
Later on in life, Robert Mitchum, who was usually indifferent to such matters, said that Charles Laughton was his favorite director and indicated that this was his favorite of the movies in which he had acted.
Producer Paul Gregory and Charles Laughton presented key members of the crew, like cinematographer Stanley Cortez, each with a 1% interest in the film. This was given to them on top of their salaries and is something that is never done. Gregory and Laughton said it was not done to encourage the artists, but to reward them for their artistry. This was done over the objections of United Artists.
Dutch-born American serial killer Harry Powers (né Herman Drenth) was the inspiration for the Preacher.
While the poor critical reviews are often cited as the reason Charles Laughton never directed another feature, Laughton himself said that he much preferred directing in the theatre. There, you could constantly change and amend the production--adding lines, changing lighting and sets--but with film once it was done it could never be changed.