During the four decades between the opening of the Civil War and the close of the nineteenth century, the United States became in many respects an economic unit. The passage of the Interstate Commerce Act in 1887, for instance, was an early recognition of the fact that the transportation problem of the nation transcended state bounds; the Sherman Anti-trust law of 1890 arose from the realization that commercial and industrial unity were rapidly coming to pass; the American Federation of Labor brought workmen from all states and many trades into a single organization.