Before the rail roads, people didn't do all that much travelling from A to B, unless they were very wealthy or had some external pressure like the need to find work or religious persecution, they mostly stayed at A. Which makes the invention of rail roads even more impressive in my eyes, it created demand rather than addressing it.
What moved from A to B was coal, ore, wheat, manufactures, but mostly by rivers. You can see this on a good map of northeast U.S. -- ask yourself why Pennsylvania is essentially rural in its center, with large cities at both ends, or why New York State is essentially rural 50 miles from the Hudson. Inland water transport was so important that the major capital projects of the early 19th century were canals.
The initial advantage of railroads over barges wasn't reach but speed. By moving goods faster, merchants were able to sell and receive payment faster, no small thing when credit was scarce, uncertain and expensive. I expect the initial rail lines served the same markets as the canals (that's where the business was), then began to extend their reach with spur lines.
There was probably some rail demand creation as the roads extended into the West -- farmland near a railroad was no different than that 20 miles away in anything but railroad proximity. But that was later, after the technology's dynamics were well understood and the players well capitalized.
