Railroads were very important to the growth of the United States because they allowed people to travel to regions that they'd never been able to go to before. Therefore, this kind of travel opened up the ability for people to settle in these new places. Also, railroads allowed the the transport of of all kinds of goods to these new places, which opened up new possibilities for businesses to sell goods and to open new stores in these places.
Railroads were crucial to the growth of the United States as it allows transportation of goods to other places, that lead to more and more trading of goods, which can improved the efficiency of business and explore endless possibilities in this big and urban cities like the US. So, a shorter time is needed to transport goods from one place to another, so it won't spoil or rot easily. It improves tourism as people can explore new horizons and unearthed new experiences that they never seen before in their life.