They helped contribute because they helped transport goods, which led to corporations getting their product out to a large selection of people.
Secondly, many people wanted to own the railroads, so many people figured out ways to do that and make money. They would either use horizontal integration, an example would be by owning all the steel companies. Or they would use vertical integration which involved owning everything from the ground up, so the wood, the steel, the wheels, everything but only a small selection of each on.
So you see, railroads really helped with modern corporations and shaping them into how the work today.