According to a news item in the Hollywood Reporter, Cecil B. DeMille directed much of the film from a stretcher, because of an operation he had months earlier. However, studio records indicate DeMille collapsed from the strain of directing three units simultaneously, and used a stretcher for about two weeks.
One of the railroad men ticks off a list of things that had been deemed "impossible," one of them being Moses' parting of the Red Sea - a winking reference to DeMille's earlier silent version of "The Ten Commandments."
The world premiere in Omaha, Nebraska, was a three-day celebration that drew 250,000 people, doubling the population of the city and requiring the National Guard to help keep order. The special train en route from Hollywood to Omaha, carrying Cecil B. DeMille and stars Barbara Stanwyck and Joel McCrea, took three days and made stops along the way, drawing large crowds. The film was shown in three theaters simultaneously; President Franklin D. Roosevelt was reported to have started the premiere proceedings by pressing a button in Washington, DC, which opened the civic auditorium. An ad stated that the premiere, which involved parades, radio broadcasts and a banquet, was the biggest in motion picture history. An antique train continued on a 15-day coast-to-coast promotional tour, stopping at 30 cities around the country.
The company had rented many local pinto horses for the filming of the Indian attack on the train. During filming, however, local cowboys had to be hired to round up the horses, as they would scatter and sometimes stampede because of the noise and confusion of these scenes - all the shooting, yelling, and yards of unfamiliar cloth on the horses, along with kettles and other implements tied to their manes and tails, made them extremely nervous and uncomfortable, and it didn't require much to make them bolt.
Dick Allen (Robert Preston) asks, "Where does he keep his 'Rule G'?", meaning a bottle of whiskey. This is a reference to Rule G: "The use of intoxicants or narcotics is prohibited", one of twelve 12 rules in standard code adopted by the Association of American Railroads.
According to Lucius Beebe's book "Union Pacific" the gold spike was not "driven" in. Since a spike made from gold would be much too soft to drive into a railroad tie the spike was "driven" into a hole drilled in a specially prepared tie. This was done both in reality and for the movie. Following the ceremony the spike was pulled out (by hand)and a new tie was put down and an iron spike was driven in.
Nearly all the antique railroad equipment used in the film was purchased by Paramount from the Virginia & Truckee Railroad in Nevada. It was used in a number of other western films over the years, and sold off in the 1970s when the population of westerns dwindled. The majority of it is now preserved at the Nevada State Railroad Museum in Carson City.
Star Robert Preston, who played important roles in several DeMille productions, not only disliked the director personally but felt he was inept at directing actors. The scene where Preston, Stanwyck, and McCrea are trapped in the boxcar took two weeks to film and, according to Preston, DeMille had nothing but "Action," "Cut," and "Print" to say to the actors. He didn't seem to care about scenes that did not include action or spectacle. When Preston became a bigger star, he turned down offers to appear in other DeMille films and avoided any relationship or contact with him.