Set prior to the start of the Civil War but after the South has seceded from the United States, Kansas Pacific centers on the efforts to build a railroad across Kansas toward the West Coast. Southern sympathizers attempt to sabotage the railroad construction efforts so Army Captain John Nelson (Sterling Hayden) is brought in to keep the project going. Captain Nelson must not only contend with the efforts of the saboteurs but also try to romance the railroad foreman's daughter, Barbara Bruce (Eve Miller). This film also features Clayton Moore, best known for his portrayal in films and on television of The Lone Ranger.