J. Edgar Hoover protested this film being made and demanded that changes be made to the script to depict the FBI in a better light (see below). Shortly before his death he recorded a disclaimer to the film; it can be heard (spoken by an imitation voice) after the closing credits. The film depicts John Dillinger being shot outside the Biograph after he pulls his gun; in fact, Dillinger never pulled a gun that night. The FBI decided they were going to kill Dillinger rather than attempt to take him alive; they announced their presence, he turned to run, and was shot six times in the back.
When John Dillinger talks to reporters while being escorted through the Lake County Jail in Crown Point, Indiana, he shakes the hand of an "anonymous" woman and talks about how he likes the chief of police and the warden. In real life, the woman was Sheriff Lillian Holley who was the the chief of police and the warden of the prison from which Dillinger made his famous "wooden gun" escape.
John Milius: "I got very expensive as a writer, so I was able to make a deal with AIP, who'd have never been able to buy one of my scripts. I said I'll write whatever you want if I can direct it. I'd have paid them to direct. I looked at the gangsters of the time, and the one that had the most appeal was John Dillinger. It was a subject I never would have chosen myself, but it allowed me to show how good I could do a gunfight, make the stuff cut together, make the story hold up, and make the actors act... I like it (the violence) because it's real. There are consequences in "Dillinger." You rob a bank, people are going to start shooting, and people are going to get hurt and shot. They run over a woman leaving the bank because that's what they did. They were desperate. But you don't dwell on it. You don't dwell on the bullet hole and blood pulsing out."
The real Biograph Theater in Chicago, where John Dillinger was killed, was one of the longest-serving movie theaters in America. Built in 1914, it finally stopped showing movies in July 2004, when it was closed for renovation to a stage theater.
When Dillinger is locking up the guards during his "wooden gun" jail break from Crown Point, one of the guards asks "Where did you get that?" (meaning the gun). To which Dillinger replies "From my lawyer." In real life, many historians have uncovered evidence that John Dillinger's lawyer, Louis Piquett, made arrangements with Homer Van Meter and Baby Face Nelson to bribe a guard to smuggle a real gun to Dillinger for his escape. But the guard chickened out and gave Dillinger a wooden gun to bluff his way out.