This movie is a favourite of F.B.I. Special Agent Dale Cooper in Twin Peaks (1990). As he states the first time he uses his tape recorder December 25, 1967: "Above my bed on the wall is my most important personal item, a poster of Jimmy Stewart in the movie The FBI Story which only I can touch."
Two FBI agents were on the set at all times.
J. Edgar Hoover personally chose James Stewart for the role of Chip Hardesty because he felt that Stewart conveyed a positive image.
J. Edgar Hoover forced director Mervyn LeRoy to reshoot a scene because he didn't approve of one of the extras.
The Jack Graham airliner bombing piece is basically correct, and Graham's real name is used.
J. Edgar Hoover: sitting at his desk in his office during the airline bombing segment. Clyde Tolson walks into the shot.