In a crucial decision rendered by the United States Supreme Court, the Standard Oil Company of New Jersey was declared an unreasonable monopoly violating the Sherman Antitrust Act. The case was pivotal in shaping antitrust law in the United States and marked a significant confrontation between the government and large corporations. The Supreme Court's ruling came after years of investigation into the company's monopolistic practices that suppressed competition and manipulated oil prices across the nation. The court's decision mandated the breakup of Standard Oil into 34 separate entities, which included companies that would later become known as Exxon, Mobil, and Chevron among others.

This legal battle was spearheaded by then-Attorney General George W. Wickersham, who sought to end the company's dominance in the oil market. Standard Oil, founded by John D. Rockefeller, had grown to control a vast majority of the oil and gasoline refining and distribution, illustrating the extreme concentration of corporate power. The case highlighted the federal government’s role in regulating large corporations, providing a legal framework that would inform future antitrust cases.

The ruling established important precedents for antitrust litigation, particularly in defining monopolistic practices and the scope of the government's regulatory powers. It signified a shift in the government's willingness to take action against powerful corporations that threatened fair competition. Following the dissolution, competition in the oil industry increased, leading to lower prices for consumers and fostering innovation in energy production and distribution methods.