Filmed in 1950, not released until 1952. According to director Richard Fleischer, when the film was finished RKO Pictures owner Howard Hughes heard good things about it and ordered that a copy of it be delivered to him so he could screen it in his private projection room. The film stayed in the projection room for more than a year, apparently because the eccentric Hughes forgot about it.
In preference to removing various walls from the sets, director Richard Fleischer decided to make extensive use of a handheld camera that could be brought into rooms; this was one of the first films to do so. To save money the train sets were rigidly fixed to the floor, and the camera was moved to simulate the train rocking.
Other than a brief scene in which a phonograph is playing, there is no music in the soundtrack.
The film was shot in 13 days and the only part actually filmed on board a train was a few seconds of the arrival in Los Angeles.
The route the train takes is the route of the old Santa Fe Railroad. The Amtrak Southwest Chief takes that same route as of 2009.