Factual error: Laredo drives the ship out of the starship docking station and scrapes the main hull on the walls. This would not be possible without either scraping the wings first, as they are much wider than the main ship, or turning nearly sideways, which they clearly don't.
Factual error: When they show the capital building in Washington DC it is still under construction, but it was actually finished in 1864 - 5 years before the movie's set.
Factual error: In the scene where the Iron Giant is spinning the boy around in a junk car he is holding, notice that the car resembles a 1959 Cadillac...however since the film is set around 1957, this is not a likely car to be found anywhere yet, much less a junk yard. (00:46:20)
Factual error: When the bloke's head gets cut off in the beginning by the circular saw blade being thrown, surely there would be more blood, like when his mom got killed under the bed?
Factual error: The TV station in the movie is KGSC channel 10, and the building shown at the beginning for the exterior shots is in fact Santa Barbara's TV station, but it's channel 3 and its call sign is KEYT. There is no channel 10 in Santa Barbara. In fact, the only channel 10 in Southern California is in San Diego. (00:01:45 - 00:34:45)