Standard Oil gradually gained almost complete control of oil refining and marketing in the United States through horizontal integration. At that time, many legislatures had made it difficult to incorporate in one state and operate in another. As a result, Rockefeller and his associates owned separate corporations across dozens of states, making their management of the whole enterprise rather unwieldy. In 1882, Rockefeller's lawyers created an innovative form of corporation to centralize their holdings, giving birth to the Standard Oil Trust. The "trust" was a corporation of corporations, and the entity's size and wealth drew much attention. Despite improving the quality and availability of kerosene products while greatly reducing their cost to the public (the price of kerosene dropped by nearly 80% over the life of the company), Standard Oil's business practices created intense controversy. The firm was attacked by journalists and politicians throughout its existence, in part for its monopolistic practices, giving momentum to the anti-trust movement.
One of the most effective attacks on Rockefeller and his firm was the 1904 publication of The History of the Standard Oil Company, by Ida Tarbell, a leading muckraker. Tarbell's father had been driven out of the oil business during the South Improvement Company affair. Although her work prompted a huge backlash against the company, Tarbell claims to have been surprised at its magnitude. In 1911, the Supreme Court of the United States found Standard Oil Company of New Jersey in violation of the Sherman Antitrust Act and held that Standard Oil, which by then still had a 64% market share, originated in illegal monopoly practices and ordered it to be broken up into 34 new companies. Rockefeller, who had rarely sold shares, owned substantial stakes in all of them.