The document discusses how the railroad peaked in mileage in Nevada in the late 1800s but then began declining due to the rise of automobiles and other forms of transportation. It also examines the major impacts of the transcontinental railroad on connecting the east and west coasts, enabling mass migration, and both helping and harming Native American tribes and the buffalo population through the influx of settlers. The railroad played a pivotal role in the development and settlement of the American West but also had unintended negative consequences.