The key legislation aimed at war merchants and business elites in U.S. history is the Sherman Antitrust Act of 1890. This law was enacted to combat monopolistic practices and promote fair competition in the marketplace. It aimed to prevent businesses from engaging in unfair trade practices that hindered competition and harmed consumers. The Sherman Antitrust Act paved the way for subsequent antitrust legislation, and it has been used by various administrations to challenge corporate monopolies and promote a more equitable economic environment in the United States.