I believe the answer is:
industrial revolution and america's vast number of natural resources would be two of the most important factors that lead to emegance of large corproations.
The existence of modern machineries along with many natural resources allow these companies to mass-produce their goods/services and enable them to obtain large amount of profit.
Americans opinion toward the corporations were very much divided. Some of the Americans believe that corporations were an important existence to bring wealth to our country and improve our standard of living, while the others criticize their practice and unfair wealth allocation.