The fifty years of American westward expansion between the 1830s and 1880s are viewed through the experiences of the Prescott and Rawlings families, as they migrate by the Erie Canal, continue over the prairies from St. Louis during the California gold rush, suffer through the Civil War, and finally help build the railroads on the plains and bring law and justice to the frontier. Along the way they meet mountain men, journey by wagon train, deal with Native Americans, and face outlaws in the southwest.

Some stock footage from other (non-Cinerama) epics were used. The Mexican army marching past the Alamo came from The Alamo (1960) and a civil war battle was taken from Raintree County (1957). The final scenes of the modern U.S. were from This Is Cinerama (1952).

Zebulon Prescott:
O Lord, without consulting with Thee, we have sent thy way some souls whose evil ways passeth all understanding. We ask Thee humbly to receive them... whether you want them or not! Amen.

Plot holes: There is no explanation of why Sheriff Ramsey is fine in one scene and wearing a bandage on his forehead in the next, immediately following. (there was a deleted or unfilmed scene where Zeb knocked Ramsey out when the Sheriff tried to stop him from going after the train robbers).

Lyrics adapted by Johnny Mercer
Performed by Debbie Reynolds and Chorus (uncredited)