At 3:12, Brandon's arm changes position as he leans against the tree.
Snow all over the girl disappears by the time she goes through the gate with her father.
A claim was made that the original Jupiter was used in the movie. After the Central Pacific Railroad was reorganized as the Southern Pacific, the steam engine was numbered SP1195, was converted to a coal burner and then sold to the Gila Valley, Globe & Northern Railroad in Arizona. Unfortunately, it was scrapped in 1906 for $1000, so it could not have been in this movie.
Frequently the men working on the railroad are seen singing "Drill Ye Terriers Drill". This song was written and first published in 1888, long after the trans-continental railroad was completed.
The Union Pacific steam engine at the Golden Spike ceremony was the UP119, not the UP116.
In some scenes at least one of the workers can be seen hitting next to the railroad spike instead of actually driving the spike into the railroad tie.
The locomotives and rolling stock are using knuckle-type couplers which did not begin wide use until the 1890's. In the 1860's era setting of this movie, the couplers in use would have been link and pin. This anachronism is understandable as the safety issue would have prohibited the use of the era appropriate link and pin couplers.
Pony Express riders are shown under attack from Indians in 1867. The Pony Express was in operation from 1860 to 1861 when it was rendered obsolete by the telegraph.
The Central Pacific steam engine used in the sequence of the 10 mile day was a coal burner, evident by the straight pipe smokestack. All Central Pacific steam engines at the time were wood burners with a diamond stack or similar smokestack.