Which robber baron became one of the wealthiest people people in the world by creating a trust that controlled most of the oil refineries in the US?

John D. Rockefeller became one of the wealthiest individuals in history by establishing the Standard Oil Company, which created a trust that controlled the majority of oil refineries in the United States. His business practices, including aggressive consolidation and monopolization, allowed him to dominate the oil industry. This not only made him a symbol of the robber baron era but also led to significant antitrust legislation in the U.S.