There was no railroad system in the United States whose importance to its tributary country was relatively greater than was that of the Missouri River to the trans-Mississippi territory in the first seventy-five years of the nineteenth century. Through the earliest days of navigation on the great Missouri, through its use in the Civil War, the Indian Wars, Custer’s Last Stand, and its eventual demise as a major highway due to the development of the railroads, this history tells of an America that depended on rivers for expansion.