The correct answer is:
D) The towns sprang up along newly laid railroad tracks. Railroads could be built almost anywhere.
The rail network in U.S. initially it traveled short distances or nearby cities, until the first transcontinental railroad began in the year 1860 joining the east coast with California, with the Pacific coast. This allowed many towns and cities to be built along the railroad tracks since the railroad allowed the towns to access the necessary subsistence and trade inputs without the need for a river or a nearby port.
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