Factual error: Though extremely modest on today's standards, the dress worn by Clara to the hoedown shows far too much cleavage for the time. No schoolteacher would ever wear a dress like that in the 1880s.
Factual error: During the gun battle, Gary Cooper runs behind a building that has an air-conditioner or swamp cooler installed in a second-floor window. (01:17:30)
Factual error: When Glass saves the Indian girl from the Frenchmen the flintlock pistol he gets off the Frenchman fires multiple times without reload, as it does later while being chased by the Indians.
Factual error: In the scene after the Mandingo fight in the Cleopatra club, when Leonardo DiCaprio gives his slave a beer, it is served in a flip top bottle. The first flip-top closure was created by Charles de Quillfeldt in the United States, who filed for a patent on 30 November 1874, receiving patent number 158406.
Factual error: The type of book that Eli is protecting would actually be just a fragment. The complete Bible, in braille, occupies as many as 18 volumes.
Factual error: After the birth of the baby, James Stewart and "Doc" Witherspoon are discussing the course of the war. "Doc" relates that he has always lived in Virginia and that his son died at Gettysburg at Little Round Top. No Virginia regiments fought at Little Round Top - only Alabama, Texas, Georgia, and Arkansas regiments.
Factual error: After the first encounter with the Apaches, the covered wagon is headed to the Fort at full speed. The camera pans to the Apaches on the ridge and you can see a truck driving at the bottom right corner. (00:32:00)
Factual error: As Preacher and Hull ride out of town for first time, Hull offers "3 hots and a cot." Earliest reference of this term is in the 1930's.
Factual error: The evil man request 100,000 pieces of gold for ransom. Each gold piece looks to be about 10 ounces, and 100,000 of those would make the entire thing weigh about 31 tons, but 2 guys are carrying it around in a little chest throughout the movie.
Factual error: In the train scene near the start there are vapor trails from modern day jet aircraft in the sky above. (00:06:15)
Factual error: Towards the end when the cavalry uncovers the American flag, it has 50 stars.
Factual error: So the Civil War ends, and the colonel heads for Texas. It must have taken close to a decade to arrive there, for when he rides into Blackthorne, Texas, he's packing a Model 1873 Colt, and a Model 1873 Winchester.
Factual error: In the scene just before the fight at the O.K. Corral, Wyatt is talking to his brothers and Doc on the porch of the town marshal's office. There is an American flag flying behind him with 50 stars on it when in fact there were only 38 stars on the flag in 1881.
Factual error: The rifles that Jake Cutter has Paul Regret dig up are Henry repeaters, or possibly 1866 Winchesters. Either way weapons unavailable in the period depicted in the movie.
Factual error: When Wyatt (Kevin Costner) becomes the sheriff/deputy/policeman of Wichita, Kansas, you can plainly see mountains in the background - there aren't any around there.
Factual error: Near the end of the film Butch is complaining about the living conditions they have to endure - jungles, swamps, snakes, night work - and Sundance sarcastically retorts "Bitch, bitch, bitch!" In 1908 the term meant just what it literally means: "Female dog." It did not adopt its current meaning of "complain" until much later. At the time the film is set - outside the context of "female dog" - it was considered to be a serious obscenity, and it would not have been used to describe something as ordinary as someone moaning about his living conditions.
Factual error: In the final gunfight in Hasting's store, John Elder fires his six-shooting Colt to a total of thirteen or fourteen times, without requiring - or doing any - reloading whatsoever.
Factual error: The aged brave, singing his death chant, has fillings.
Factual error: John Wayne and James Caan are in the gunsmiths shop, and behind the gunsmith on the shelf are some products, one of these products is Bugler tobacco. Bugler tobacco was introduced in the United States in 1932. (01:00:00 - 01:02:00)
Factual error: When John Wayne and Geraldine Page first meet the lead cavalry man and 'Buffalo Baker', you can see in the distance a radio tower on top of the hill/mountain.
Suggested correction: It's not a radio tower. It leans to one side and also the line goes almost to the creek bed. When the troops come back after getting ambushed it's not in the picture anymore.
I'm watching the movie now and I saw the radio tower in the background and I saw no wires and the tower doesn't lean.
Suggested correction: It isn't a tower at all, it's a flaw in the film. As the scene continues, at one point you can see it kind of shake or move a little. It's just a line or flaw on the film itself, it's not a radio tower or anything in the background.