Factual error: In the very beginning (2nd scene) just after Danny (the Caddy) eats and then jumps down from the backside of his house and hops on his bike to head to work, look in the background behind him and at about the 5th house or so he passes you will see a classic palm tree in the front yard. The movie takes place in Nebraska (which doesn't have any palm trees of course).
Factual error: In an attempt to create a believable 1940s gym, it appears the production crew got hold of many contemporary boxing posters as possible. Most of these were Greeked to avoid mentioning real boxers (such as "Dave Ritlaf" and "John Paropianeo"), but one of these prominently features a "Ronnie Harris", along with a photograph. Ronnie Harris was a real boxer, but wasn't even born until 1948, 7 years after this scene was set, giving away that a poster from the '70s was used. (00:16:08)