How did the railroad industry pioneer the economic developments of the late nineteenth century? (In the U.S.)Remember, economic developments!
I would say that the major way in which the railroads acted as pioneers was in relation to building the big businesses that came to typify the late 19th and early 20th centuries. As one of the books I teach from says, railroads were the first of the truly big businesses.
As the railroads got so big, they had to pioneer new ways of doing business. Most importantly, they were the first companies to get so large that they needed complex bureaucracies to keep them running efficiently. This was the beginning of the new trend toward large companies that had significant numbers of white collar bureaucrats working for them.
One example of how the railroads had to change things is not really economic, but it illustrates the point. It was only because of the expansion of railroads that the US got standardized time zones. This was because the railroads were big, complex businesses that needed to really know for sure that each of its parts was in agreement as to what time it was. From that came the time zones.
So the railroad expansion brought with it the organization and rationalization of the activities of huge businesses.