This document summarizes the development of the railroad industry in the United States between 1865-1900. It describes how the railroad network expanded dramatically after the Civil War, driven by government subsidies in the form of large land grants. The completion of the first transcontinental railroad in 1869 connected the country by rail and spurred major economic growth and western expansion. However, the railroad industry was plagued by corruption and monopolistic practices. This led to the first attempts at government regulation through acts like the Interstate Commerce Act of 1887. The growth of railroads was central to the massive industrialization of the U.S. economy during this period.