Other mistake: When the Mafia are having a dinner party, the film cuts to Charlie Croker throwing his bicycle into the substation to cause a powercut. After the big explosion, the camera switches back to the dinner party and then all the lights go out. But before the lights go out, if you look at the end of the dinner table, there is a doorway, and you can see smoke coming from the candles which have already been lit before the lights go out. Within seconds of the power cut, these candles are brought in from doorway and another set comes in from the left-hand side. A little premature.
Other mistake: Throughout most of the film, Mattie Ross' gun is correctly shown to be a Colt's Dragoon .44 caliber revolver. However, in the scene where Tom Chaney is looking down at her from the top of the well into which she had fallen, the gun in his hand is a Colt's Model 1860 Army. Presumably, when he, too falls into the well after being shot by Marshall Cogburn, the gun goes with him. When Cogburn retrieves the weapon before helping Mattie out of the pit, the gun is once more a Colt's Dragoon.
Other mistake: In the scene when the helicopters arrive over the research center, look at the heli in the bottom right - it just fades out, while one on the left materialises, and the one in the middle changes position. Notice that after all the helicopters have changed place, you can see the helicopter that faded out appear on the helipad (02:25:25)
Other mistake: As Anne is about to be executed for adultery she begins recalling the important events of her life since meeting Henry VIII. She counts each of the wooden stakes numbered "100 Days" and recalls various events involving she and Henry. There should be 10 to account for the 1000 days but there are only nine. (02:13:00)
Other mistake: The narrator says that the train stopped to let the train filled with Christmas carolers go by, but the train passed after the train had already crossed the tracks, so there was no need to wait. (00:19:30)
Other mistake: When the government men were going to purchase the wild horses for the army, they offered to buy them at twenty five each. The Mexican men offered fifty five each, but John Wayne said he was selling them for thirty five each. So which is it? (00:30:15)
Other mistake: A group of students poses as painters so they can investigate shady doings at A.J. Arno's home. They had made a work order which included their dormitory's phone number. When Arno calls the number, he asks, "Is this 247-8824?" A student says "Yes" but the number on the phone dial is "471249624."