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Railroads, like electricity and the telephone system were regarded as a "natural monopoly" that needed to be regulated, by cities and states if not by federal government.
I believe Enterprise Denied and Railroads Triumphant by Albro Martin were supposed to be good studies of the political economy of railroad regulation.
Martin shows that regulation ruined the railroads' ability to adapt to changing situations, particularly after road transport cut into their market.
More here.