Revealing mistake: Early in the movie, there is a visible circular, plastic looking effect on Gideon's arm as he removes the bullet with the knife. This is more noticeable around his shoulder when he cauterizes his wound with the hot knife.
Continuity mistake: In the prosecuting attorney's speech in the first courtroom scene, the judge's house of cards is no more than 2 levels high (a base level with a peak) [0:2:20]. In the close-up shot of the judge, the house of cards changes to 3 levels high (2 base levels and a peak)[0:2:35]. When the scene focuses back on the prosecuting attorney, the house is back to two levels of height[0:2:39]. (00:02:20)
Factual error: The movie is set in 1882, however there is a scene where he meets Doc Brown with his DeLorean. Back to the Future Part III took place in 1885.
Factual error: The newly born foal is too dry and too steady on its legs. (00:22:25)
Continuity mistake: Sykes is shot in the right leg, in the thigh area, by the bounty hunters. We see the blood clearly on it when he sits on a rock and holds his leg. Later, when he returns to Aquaverde where he meets Robert Ryan, we see as he sits on his horse that his left leg is bandaged.
Visible crew/equipment: Michael Pate is walking down the street in this western and as he passes a shop window you can see all the camera crew, the director, the arc lights etc.
Visible crew/equipment: When Robert and Arvid are in the desert and Robert falls into the pit, you can see the shadow of director Jan Troell holding the camera.
Continuity mistake: At the dinner scene when Mattie Ross is trying to obtain Rooster Cogburn's services, Rooster clears the table, and in the next scene he re-clears the table by pushing everything aside to play cards with Chin Lee.
Factual error: The chairlift for the ski resort on Mount Hood is visible in the scene that pans to the right just before James Stewart is abandoned on the mountain. This ski resort was not around when the film is set.
Revealing mistake: When Howard and Curtin chase Dobbs, they pass a dead donkey which is obviously breathing, and the rope used to tie its legs together is visible too.
Visible crew/equipment: During the movie whenever Bob Hope is pulled off the wagon by his team of horses you can see a board leaning against the wagon that was used to help the stunt man when he was pulled off the wagon.
Factual error: Upon completing the task of lowering every wagon, horse, mule, ox and human down to the canyon floor, the settlers proceed to build rafts for their wagons..however, their scout would have informed them that they would be going overland to intercept the Columbia River to the northwest. The Snake River, with class IV rapids, (even now tamed with dams) was no place for the uninitiated to go rafting.
Plot hole: Kane and Irons abandon their horses to hook a ride on the train, leaving behind their rifles. When they get to Hadleyville, Kane has somehow reacquired his Sharps.
Plot hole: Immediately before the attack on Pony-That-Walks' village Capt. Brittles states that it's 12 minutes to midnight,and orders the attack. The attack is a surprise attack, yet all the warriors pile out of their tipi's fully clothed, painted and with their eagle feathers braided into their hair.
Revealing mistake: The baby Robert William Pedro is actually a girl. You can see it in the scene where the baby is greased.
Revealing mistake: A 'bald wig' is visible on Harry Morgan when he first arrives in Purgatory.
Continuity mistake: At Molly's party after returning from Europe, the Duchess is introduced, and everyone bows. The shot shows Molly reaching for her neighbor who's standing straight, to bow down, and she does. Then there is a long shot showing the crowd, and the neighbor is again standing, and then you see Molly reach out for her again as she just had.
Continuity mistake: When the Bannister gang begins shooting at the house, the ladies abandon their breakfast to run and hide upstairs. There's a pitcher half full of milk on the table. But a few shots later, when one of the Bannisters bursts into the kitchen, the milk pitcher is empty, and the dishes are in different positions on the table. (01:23:55)
Visible crew/equipment: In a scene where Kirk Douglas appears to 'leap' onto his horse, a crew members arm is clearly visible in the foot of the shot pushing a mini trampoline next to the horse, ready for Kirk to jump onto and bounce up onto the saddle.
Visible crew/equipment: When Caleb punches the driver guy in the bar, the guy (who has now been replaced by a stuntman) goes flying backwards and lands on the pool table. When this happens, a wire can be seen on the stuntman, pulling him back and guiding his movement.