When he first learned that Richard Brooks was interested in adapting his novel, Sinclair Lewis told him that he should change it significantly, advising him to read all the criticisms of the book and use them as a way to improve on it.
Pat Hingle landed the title role, but before filming began, he became caught in a stalled elevator in his apartment building. He lost his balance while trying to crawl out and fell 54 feet down the shaft. He sustained massive injuries, including a fractured skull, wrist, hip and leg, and several broken ribs. He also lost his little finger on his left hand. Hingle spent much of the next year relearning how to walk and was forced to give up the part in order to recover from his horrific injuries.
After this film was released, Burt Lancaster got a letter from a boyhood friend he had not heard from in years. The friend wrote him that Lancaster's part in this film was the closest to the way Lancaster acted in real life when they were kids.
In a hate-filled sermon, Gantry denounces a number of "heresies" including "Russellism". This is a reference to Charles Taze Russell, first president of the (current) Watchtower Bible and Tract Society, the legal organization used by Jehovah's Witnesses.