How did the growth of railroads american businesses expand

This demand, particularly for steel, helped the US economy to boom. Second, the railroads created a huge national market. Before the expansion of railroads, it had been very hard to get goods from place to place on land. ... In these ways, the railroad expansion allowed the US economy to expand rapidly in the late 1800s.

c. wright mills's sociological imagination suggest investigating to explain this increase?

answer; humanistic;