J. Edgar Hoover forced director Mervyn LeRoy to re-shoot a scene because he didn't approve of one of the extras.
J. Edgar Hoover personally chose James Stewart for the role of Chip Hardesty because he felt that Stewart conveyed a positive image.
According to her memoir Jane Fonda was suggested to Mervyn LeRoy for the role of Jennie by James Stewart. After meeting the director she expressed disinterest in the role which instead went to Diane Jergens.
Final film of Forrest Taylor.
In 1957 Grammercy Pictures bought the rights to a 1950 novel called "The FBI Story" by Mildred and Gordon Gordon. The Gordons claimed they had earlier submitted a script to Warners before the studio purchased the rights to Don Whitehead's book also titled "The FBI Story" for $100,000. The Gordons sued and were awarded $54,000 in damages.
Security checks were performed on all those involved on the film's production.
Supposedly, and this may have been a promotional gimmick, J. Edgar Hoover wept during the scene where Sam Crandall (Murray Hamilton) dies after being shot by Baby Face Nelson.
The character of Sam Crandall is loosely based on FBI agent Sam Cowley, who worked for Melvin Purvis and was killed in a shootout with Baby Face Nelson--who was also killed--in the Little Bohemia Raid of 1934 near Mercer, Wisconsin.
The Jack Graham airliner bombing piece is basically correct, and Graham's real name is used.
The scene in the film in which J. Edgar Hoover "personally" arrested Alvin Carpis has since been debunked as a myth created by Hoover himself. In 1936, Hoover had gone before the Senate Appropriations Commitee to get more funds to continue to build the FBI. A Senator asked Hoover if he'd ever personally made an arrest. Hoover kept trying to dodge the question but was eventually forced to answer that he hadn't (he'd joined the bureau as an Assistant Director and was promoted through the bureaucracy without ever having served in the field). Embarassed by the hearings, Hoover made it a point to follow the case of Karpis, the last of the high-profile 1930s-era bank robbers. According to Karpis himself in his autobiography "Public Enemy Number One: The Alvin Karpis Story", as he was leaving the hotel to get into his car, he was surrounded by nearly a dozen well-armed agents who forced him out of the car. As he stood there being patted down for weapons, he noticed two men peering around the corner. An agent noticed what Karpis was looking at and said, "It's okay, Chief. We got 'im." Then Hoover and his assistant, 'Clyde Tolson' (who makes a cameo appearance in the film in the same scene as Hoover) came out and Hoover dramatically showed Karpis his badge, declaring, "Karpis, you're under arrest!
Two FBI agents were on the set at all times.