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.
Continuity mistake: In the scene when John Wayne puts his reins between his teeth and his rifle in his right hand and his pistol in his left, at one point they switch hands.
Continuity mistake: After Kim Darby declines the coffee, John Wayne puts his empty plate in the middle of the table. Immediately in the next shot, the plate is back in front of him with some scraps of food still on it.
Factual error: Campbell is armed with what is described by Wayne as a "buffalo gun", a large bore rifle known for its power and substantial recoil. Campbell shoots a wild turkey with the gun and causes the meat to be severely damaged. Wayne comments, "Too much gun" emphasizing the power of the gun. However, when Campbell shoots the turkey with this "buffalo gun" there is no visible recoil.
Continuity mistake: Near the end of the movie, after Rooster and Mattie's horse has collapsed, Rooster begins to carry Mattie. You can see that Mattie's blouse has come untucked from her skirt. However, once Rooster has acquired the wagon, Mattie is laid across his lap and her blouse is now tucked back into her skirt.
Factual error: There are no snow-capped mountain peaks anywhere near Ft. Smith, Arkansas. They appear to have chased Ned Pepper all the way to the Rockies, 500 miles or more away.
Factual error: On the second day of the trio's journey from setting out from Ft. Smith Arkansas the scenery jumps to the landscape of the Black Mesa near Santa Fe New Mexico. The credits substantiate that indeed some scenes were shot in this area. Ft. Smith is 729 miles from Santa Fe. The terrain near Ft Smith is mostly wooded for hundreds of miles.
Continuity mistake: When Rooster and LaBeouf ride the ferry across the river, Mattie swims with her horse. When they meet on the other side moments later, she and the horse are dry as a bone. Her clothes should have been dripping wet.
Continuity mistake: When Rooster is walking out of the court room and meets Mattie on the stairs, his bow tie is different, or tied differently than the one he is wearing when he is being cross-examined.
Factual error: LaBeouf is repeatedly said to be from El Paso, yet the crime for which he is pursuing Tom Chaney occurred in Waco - 547 miles away from El Paso.
Answer: The mountain in the background appears to have two vertical grooves down the surface facing the camera. Those grooves are far too wide to be ski trails. They are simply a natural part of the mountain. Mountains are subjected, over hundreds of thousands of years, to a variety of natural forces, such as wind erosion, water erosion, tectonic shifts and earthquakes, just to name a few. These cause mountains to have irregular shapes, and irregular surfaces.
Michael Albert