Factual error: In the beginning of the movie there is a shot of the flag being raised over Fort Stark and the sound of a bugle is playing. The bugler is playing "Retreat" which is only played when the flag is coming down; he should be playing "To The Colors".
Factual error: In the very beginning of the movie, the narrator says, "Pony Express riders know that one more such attack (referring to the Custer Massacre) would mean a hundred years before another wagon train crosses the prairie." Then they show a Pony Express rider supposedly carrying the news. But the Custer massacre happened in June of 1876, and the Pony Express went out of business in 1861.
Factual error: It opens indicating that Custer is dead. Which would be June 25, 1876. They show a calendar showing a month starting with a Wednesday with 31 days. In 1876 only March started with a Wednesday and had 31 days. When Nathan Brittles is retiring, Olivia Dandridge is attempting to leave the fort before winter sets in, which doesn't fit March.
Factual error: The inscription on captains Brittle's silver watch was "lest we forget." That quote was taken from a Kipling poem written while he lived in America in 1897. Earlier in the film it referenced the Custer defeat at Little Bighorn that happened in 1876. The watch sentiment inscribed was not written for another 21 years.
Factual error: A few minutes after marking off days on an 1876 calendar while preparing for retirement, John Wayne states that when he had left his father's home (when young) he was wearing blue jeans. Blue jeans weren't invented until 1873.
