This movie musical directed by Francis Ford Coppola stars Fred Astaire and Petula Clark as two Irish immigrants who come to save a small southern town from greedy landowners. 

Early in the film there is a musical montage as we see Woody (Don Francks) riding the train cross-country. This was filmed on the Sierra Railroad in Tuolumne County, CA. We catch a glimpse of him in the cab of Sierra #3 and on and in several of the cars including Combine #5 and Caboose #7. As the song ends we see a wide shot of the train going across a valley (with a much different consist).

Later we see Finian (Astaire) arriving to the fictional Rainbow Valley on train full of goodies for the townsfolk. The town and narrow-gauge railroad line were apparently constructed on the backlot at Warner Brothers.