Final answer:
John D. Rockefeller expanded the Standard Oil Company through horizontal integration, vertical integration, and the creation of trusts, which allowed him to monopolize the oil industry and outcompete rivals.
Step-by-step explanation:
American industrialist John D. Rockefeller expanded the Standard Oil Company using a variety of business strategies, most notably through a technique known as horizontal integration. By merging with or acquiring other oil companies, and also forming trusts to control these companies indirectly, Rockefeller rapidly increased his market share. He also engaged in vertical integration, taking over every step of the oil production and distribution process, which allowed him to further lower costs and outcompete rivals.
His aggressive tactics included making secret deals with railways for favorable shipping rates, which aided in driving his competition out of business. Over time, these methods enabled him to control a vast majority of the oil industry.