What business structure allowed a monopoly over the American oil industry

"John D. Rockefeller and the oil industry. John D. Rockefeller created Standard Oil of Ohio in 1870, and the company quickly monopolized oil refining and transportation in the United States. Rockefeller received significant rebates from the railroads and made his own oil barrels, built pipelines and oil storage facilities, and bought tank cars to reduce expenses. These methods of vertical integration allowed Standard Oil to cut prices and drive competitors out of business. The company also led the way in horizontal integration, controlling businesses in the same industry. In 1882, Rockefeller formed the Standard Oil Trust, which controlled upward of 95 percent of the refining capacity in the United States. In a trust, stockholders give up their stock and the control of their respective companies to a board of trustees in return for trust certificates, which pay higher dividends."