Final answer:
John D. Rockefeller acquired nearly complete control over the oil industry through the strategic use of horizontal integration with his Standard Oil Company. He merged with or undercut competitors, formed trusts, and practiced vertical integration to control nearly every aspect of the oil business.
Step-by-step explanation:
John D. Rockefeller utilized horizontal integration with Standard Oil Company by systematically merging with other oil firms or driving them out of business through aggressive pricing strategies. He created trusts, which were conglomerations of smaller companies, allowing him to centralize control over the oil industry. Rockefeller's Standard Oil came to dominate the oil market by setting high oil prices once he had eliminated his competition.
Moreover, his influence grew further when he applied vertical integration, taking over each aspect of the oil product lifecycle to reduce costs and increase control. The result of this integration was impressive: by 1879, Standard Oil controlled about 95 percent of the oil refining businesses in the United States.