Other mistake: The objective of the band is a cache of gold hidden some years ago in the firebox of a wrecked locomotive in the wilds of Northern Mexico. When they finally dig the firebox door out and open it, the strongbox is sitting inside a completely clean firebox, with nary a cinder, ash, or chunk of burned wood in sight. If the loco and cars had been abandoned after the derailment, there would still have been residue in the firebox.
The Train Robbers (1973)
1 other mistake
Directed by: Burt Kennedy
Starring: John Wayne, Ann-Margret, Ben Johnson, Rod Taylor
Genres: Western
Factual error: Anne Margaret is seen changing into pants, and as she's shown stepping into the pant leg she is wearing white pantyhose. Pantyhose wasn't invented at this time.
Sam Turner: All we want to know is what we rode here for.
Lane: What a gun rides anywhere for - money. The more of it the more chances you take.
Answer: It was established that railroad tracks were put through the desert. Probably a shortcut to save time or it was the only area they were allowed to build. Land deals, claim jumping and protected grounds were a big part of where tracks could be laid. It was after the train disaster that the tracks were discontinued.