The kitchen staff for the film was made up largely of Chinese cooks. Some of them had been workers on the transcontinental railroad in 1869, the same construction project that forms the basis of this film.
A notation on a title card states that in the final scenes of the meeting of the west and east railways, director John Ford used the actual engines that did meet on that day, the Jupiter and Locomotive 116. This claim was, in fact, not true. Not only were neither of the engines the original ones, but one of the actual engines had been dismantled for scrap many years before.
During the filming of a climactic gun battle, which took several days to film, the cast and crew awoke to find that an unexpected snowfall had blanketed the set. The crew, and most of the cast, set to work clearing the large set of the fresh snow, and amazingly were able to do so in about an hour.
According to R.L. Hough, about 35 of the many extras were retired, elderly Chinese-Americans who had previously had decades-long careers working for the railroad. Hough described them as "wonderful" to work with.
During the title sequence before the film starts, a dedication is given to George Stephenson the father of the railway locomotive. Unfortunately it describes Stephenson as Scottish, when in fact he is an Englishman, born in Wylam Northumberland in 1781.
When on location, the crew built a large town set in which many of the buildings had practical rooms. These rooms soon became living quarters, holding areas and storage space. The editing lab was set up in the post office set.
The VHS version published in Argentina by "Epoca Video Ediciones" was lifted from an Italian video version that, in turn, was lifted from a Paul Killiam print with the titles (except the original credits) replaced with Italian translations. "Epoca Video Ediciones", subtitled that print in Spanish and made an important mistake that they have never corrected: the film was originally released in Argentina as "El caballo de hierro" but they put "El caballo de acero".