Factual error: In the drugstore scene where Mary whispers in George's bad ear, there are several shots showing a Coca-Cola thermometer on the wall where George hangs his jacket. This particular scene was to have taken place in 1919, but this particular thermometer wasn't produced until 1939.
Factual error: Tombstone is nowhere near Monument Valley.
Factual error: During "On the Atchison, Topeka and the Santa Fe", the train depicted is a Baldwin-built 4-4-0 no. 49, the "Wm. B. Strong." The actual AT&SF no. 49 was a 0-4-0 named "Vulcan", built by Hinkley in 1876. "Wm. B. Strong" was actually AT&SF's second no. 2, and was built in their Topeka shops in 1881.
Factual error: Fred would not have been a captain without prior college education. He was previously a soda jerk and would have been enlisted.
Factual error: When the camera pans to the theatre right after the opening credits, the sign uses the British spelling of "theatre" instead of the American "theater."