In the opening scene where the train comes into town it goes past the water tank, in the next scene the train is parked at the tank taking water.
On arriving in town, Grady takes a shower from the railway's water tank. He is thoroughly soaked top to bottom, including the back of his shirt sleeves and the whole of his shirt front. Yet, in following shots, parts of his shirt are dry. Notably the back of his sleeves and the front of his shirt where it is covered by his vest.
After Lane shoots the lock on the chest, when he lifts the latch the lock has completely disappeared without anyone removing it. Shooting the lock would not have caused it to disintegrate.
Opening scene: Mrs. Lowe and Lane walk towards Grady & Calhoun, Mrs. Lowe and Lane cast shadows towards the rail track (left to right across the screen). Then the sky is overcast and the earth behind them is in shadow. It was in full Sunshine before.
When they meet, Calhoun & Lane negotiate "Why we're here." In long shots, Calhoun's vest (waistcoat) flaps in the wind. In close up, it hangs straight and undisturbed.
During the era depicted, the price of gold in US dollars was fixed at $20.67 per troy ounce. $500,000 worth of gold would therefore weigh about 750 kg or 1,660 pounds avoirdupois - far too much for one man to shift or for one mule to carry, as depicted in different scenes.
(At about 30 mins) When the group is coming into the town modern power poles are visible in the background.
When the Pinkerton man is shooting at Lane and his cronies there is a group of outlaws plainly visible to his right, yet they ignore him.
In the opening scene of the movie when they show you the town from a distance on a windy day, dust is only blowing from behind the buildings, and not on the roads and open areas, indicating hidden wind machines.
When Wayne and the group cross the river before returning to town a car can be seen driving in the background.
During the shootout at the abandoned railroad crash site, when John Wayne is talking to Ann Margret, tire tracks can be clearly seen in the sand.
As the train full of horsemen pulls into the station, there is a brief shot of the back of the stock car and it has steel ends, which was not common practice until the early twentieth century.
As the gang is searching for a sand-covered railroad track in a sand storm they have yet to find anything. Yet behind them, to the right of the picture, as the camera moves to the right slightly, we get a clear view of the camera dolly track, shiny and sand-free.
In the opening sequence the depot sign indicates that the town is Liberty, Texas. This town actually in southeast Texas near Houston. There are no mountains in the area and the nearest desert is several hundred miles to the west.