Final answer:
Standard Oil was broken up in 1911 due to violating antitrust laws, specifically after the U.S. Supreme Court upheld the government's use of the Sherman Antitrust Act. Additional antitrust measures continued with the Clayton Act and the creation of the FTC.
Step-by-step explanation:
The government broke up Standard Oil in 1911 due to its breach of antitrust laws. The U.S. government sought to limit the power of large trusts through legislation such as the Sherman Antitrust Act of 1890, the nation's first antitrust law. Standard Oil, which controlled approximately 90% of the country's oil refining, was a prime example of such power being consolidated into a trust, ultimately leading to the Supreme Court upholding the government's decision to break the company into 34 independent firms, including names like Exxon, Mobil, Amoco, and Chevron. Further enforcement of antitrust laws continued with the Clayton Antitrust Act of 1914, which outlawed mergers and acquisitions that would substantially lessen competition, and the introduction of the Federal Trade Commission (FTC) to better define unfair competitive practices.