What brought john d Rockefeller monopoly to a end in 1911?

John D. Rockefeller's monopoly, primarily through the Standard Oil Company, came to an end in 1911 when the U.S. Supreme Court ruled that the company violated the Sherman Antitrust Act. The court ordered the dissolution of Standard Oil into 34 smaller companies to restore competition in the oil market. This decision was a significant moment in U.S. antitrust law, marking a shift towards regulating monopolistic practices. The breakup of Standard Oil helped to promote fair competition and consumer choice in the industry.