By 1877 john d. rockefeller controlled 90 percent of oil refineries in the united states because of

John Rockefeller controlled 90 percent of the oil refineries and pipelines because of him starting his own oil company called Standard Oil of Ohio, and with this company he grew it to be the largest oil refinery in Cleveland, Ohio. He then started to expand his business by buying out rival refinery companies as well as developing companies to distribute and market its products. Eventually by 1882, having now control 90% of the oil business, these combined companies would be known as the Standard Oil Trust. I hope this helps :)