Inger Stevens had never heard of Clint Eastwood before she was cast. Once they met she began to like him very much and they ended up having an affair during filming. When the film was finished, Stevens told director Ted Post: "Anytime you do a picture with Clint and there's a part in it, call me."
Clint Eastwood's first leading role in a Hollywood film. He was already 38 years old. Hang 'Em High is also notable for being Eastwood's first assignment as a producer. Having formed Malpaso (it means "bad step" in Spanish and Eastwood liked the irony) Productions with his friend Leonard Freeman as a loan-out company to help struggling independent filmmakers, Eastwood never dreamed it would develop into a full-scale production house.
Clint Eastwood (Marshal Jed Cooper) wore the same gun belt and holster that he (as "The Man with No Name") wore in the "Dollars" trilogy (the three "Spaghetti Western" movies directed by Sergio Leone), and that he also wore as Hogan in Two Mules for Sister Sara (1970).
Reportedly, producer Leonard Freeman clashed with director Ted Post during production. One day Freeman showed up on the set, issuing orders and taking charge. Post wanted to confront him, but Clint Eastwood intervened. Eastwood spoke to Freeman, and Freeman left the set and didn't return. What he said was, "If you show up on this set again, there won't be a set ... won't be a cast, won't be a crew."
The exterior scenes of Fort Grant and the courthouse were shot on MGM's famed Western Street, on Lot #3; a popular location for movie and television settings. Several The Twilight Zone (1959) stories were shot on this set because it could pass for a "cowboy"-style town, as well as a turn-of-the-century urban street. Similar sets on the same lot were Billy the Kid Street and Ghost Town Street.