On May 15, 1911, the U.S. Supreme Court ruled that the Standard Oil Company was an illegal monopoly under the Sherman Antitrust Act. The Court ordered the company’s breakup into smaller, independent firms. Standard Oil, controlled by John D. Rockefeller, had dominated the oil industry through tactics that critics said reduced competition. The ruling affirmed the government’s power to regulate large corporations in the public interest. Many of the successor companies later grew into major oil firms in their own right. The case remains one of the most important antitrust decisions in U.S. history.
