There were several factors that led to the growth of the railroads. One was the movement of people to the West. As people moved to the West, they needed a way to get materials and products to the area. The railroads expanded to fill this demand. People went west to mine, farm, and raise sheep and cattle. They needed basic supplies in order to survive. Plus, the farmers and cattle ranchers needed to ship their products. The railroads provided a way for this to occur. It allowed the railroad owners an opportunity to make money.
The government also encouraged the growth of the railroads. The Pacific Railway Act authorized the building of the transcontinental railroad. The government worked with railroad companies to make railroad growth happen. One thing the government did was give land grants to the railroad companies. The companies would sell this land and use the money they received to build the new or extended railroad lines.
As our trade expanded, railroad growth was needed. Railroad operators who figured out how to fill their trains with products and people as the trains traveled from the East to the West and vice versa could make a lot of money. This involved interstate trade as well as products we received from trade with other countries.