Shortly after the three riders enter the desert, Hightower discovers that Pedro's water bag is empty and throws it away. As they ride away in a long shot, the water bag is still visible on Pedro's horse.
When the three Godfathers leave the covered wagon with little Robert William Pedro, the canvas is coming loose in the wind. Later, when Purly Sweet and his posse arrive at the covered wagon, the canvas is tied down firmly.
When the train stops in town, the tender is correct. When it is shown running in the desert, the tender is incorrect. It is an oil tender and is incorrect for that time period. The fuel would have been wood.
The coach car of the train in Welcome has seven windows, no roof-walk and the number under the windows. The car at Mojave Tanks, which is supposed to be the same, has five windows, a roof-walk and the number in front of the windows. The five-window car also has no interior, as seen through the rear door.
In the chase scenes after the bank robbery, the shadows change direction repeatedly, indicating the scenes were shot at different times of the day.
What appear to be power lines are visible overhead behind Ruby Latham when the stagecoach is stopped in Welcome, Arizona. They were intended to be interpreted as telegraph lines.
The baby that Hightower is greasing, who is supposed to be a boy, is played by a girl.
Near the end of the movie, Hightower reads a Bible passage from the book of Matthew, yet the Bible is opened close to the beginning.
When Robert Hightower (John Wayne) stumbles into the New Jerusalem saloon, the people are singing "The Holy City". Although the time-setting is unclear, the women's fashions indicate it is in the 1870s. "The Holy City" wasn't written until 1892 and didn't become popular until around the turn of the century (1900).
When Pedro is using the rattle, it can be heard even when he stops shaking it.
When Ben Johnson is standing in the buckboard when the sheriff and three deputies use it to chase the three bank robbers out of town, he has one leg behind him, bracing himself to stay standing while the horses gallop. There is a strap secured to the tray of the buckboard and he has the toe of his boot wedged in it to help keep his balance.
While Hightower is holding the baby at the wagon, Pete is asked if he got any information about looking after the baby from its dying mother. He is supposed to say, "Do you think I was going to drive the lady crazy?" What he says is, "Do you think I was going to drive the lazy crazy?"