The Vatican bankrolled some of the film, and the Vatican liaison was a young Joseph Ratzinger, who in 2005 became the 265th Catholic Pope as Benedict XVI.
Although the movie is fiction, parts of the story were based on the early career of Cardinal Francis Joseph Spellman, Archibishop of New York from 1939 to 1967.
Tom Tryon was nominated for a Golden Globe in 1963 for his performance, but suffered immensely under Otto Preminger's notorious abusive treatment of actors. At one point during filming, Preminger fired Tryon in front of his parents when they visited the set, then rehired him after being satisfied that Tryon had been sufficiently humiliated. This type of treatment was a big turning point for Tryon, who eventually retired from acting and turned to a successful writing career.
Final film of Dorothy Gish.