According to director John Sturges' commentary track on the Criterion laserdisc, this film was also shot simultaneously in a standard 4:3 ratio version (as well as CinemaScope), because MGM executives were unsure of the wide-screen version. It was never released.
The opening shot with the train was added after preview audiences did not like the original version. The sequence was created by filming with a helicopter flying away from the train and running the film backwards. (Source - audio commentary by John Sturges on Criterion laserdisc.)
The projectionist's records have revealed that over the years this has become one of the most frequently shown films in the screening room of The White House.
According to one biographer of Spencer Tracy, the script did not originally call for the lead character to be a one-armed man. The producers were keen to get Tracy but didn't think he'd be interested, so they gave the character this disability with the idea that no actor can resist playing a character with a physical impairment.
The script called for Spencer Tracy's character to light matches one-handed. Tracy had difficulty with this and convinced director John Sturges to let him use a Zippo lighter, as every veteran he ever met had one.
In the original short story, MacReedy brandishes a Beretta and brags of his prowess with it, but in the movie, he uses judo - an idea meant to suggest that MacReedy is Japanese-American.
The sign behind the hotel desk is a quote from English evangelist John Wesley: "Do all the good you can, By all the means you can, In all the ways you can, In all the places you can, At all the times you can, To all the people you can, As long as ever you can."
Exteriors for this film (particularly the trip to "Adobe Flat") were filmed in and around Lone Pine, California (a location often used by other films). The Japanese farmer central to the plot was (supposedly) sent to an (unnamed) internment camp after Pearl Harbor. Coincidentally, Lone Pine is just five miles from Manzanar, the best known internment camp. Present-day visitors may inspect both the Alabama Hills and Manzanar locations.