The information below ( with the exception of "the Ballad of the Iron Horse")
is taken from Wikipedia.
The film presents an idealized image of the construction of the American first transcontinental railroad. It culminates with the scene of driving of the golden spike at Promontory Summit on May 10, 1869. There is a note in the title before this scene that the two original locomotives from 1869 event are used in the film, although this is false - both engines (Union Pacific No. 119 and Jupiter) were scrapped before 1910. Of course, a romantic story with love, treachery and revenge is also here. Main stars were George O'Brien and Madge Bellamy.
In December 2011, The Iron Horse was selected for inclusion in the Library of Congress' National Film Registry. In choosing the film, the Registry said that The Iron Horse "introduced to American and world audiences a reverential, elegiac mythology that has influenced many subsequent Westerns."
Among the extras used in the Central Pacific sequences were several Chinese playing coolies who worked on the railroad. They were in fact retired Central Pacific Railroad employees who had helped build the first transcontinental railroad through the Sierras, who came out to participate in the filming as a lark.
Ballad of the Iron Horse