Rockefeller and the Oil Industry

In the period following the Civil War, the United States saw a rapid expansion of industry and capitalism. This transformation led to significant economic changes, as well as the rise of influential businessmen who played key roles in shaping the nation's economy. One such individual was John D. Rockefeller, who founded a company that became synonymous with a particular industry. Which industry did Rockefeller's company dominate, leading to his status as one of the wealthiest individuals of the era?