Railroads did several things for the country, including making it smaller in a way, creating a national market, driving the economy and opening vast expanses of America that were not easily reached before the railroad. The railroad was a key piece of moving America forward and making the country grow.
With the ability to ship things from one side of the country to the other in a matter of days or weeks instead of months, the American economy grew. Around the time that the railroad was completed in the late 1800s, the technology in America was growing as well. Before the turn of the century, railroads had refrigerated cars that made it possible to ship items that normally would have spoiled before.