The railroads were primarily used to ship manufactured goods from Ohio to the Eastern and Southern markets and ship raw materials to feed those factories.  Shipping raw materials to the factories in the Northeast, e.g., coal, was also a factor.

The North didn't have the river systems.  A "fake" river system - canals - were used but rail roads out competed them when the goods had to be transported farther than 200 miles.  

For passenger service the railroads won hand's down.  

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre