What percentage of the oil business did John D Rockefeller control?

At the height of his influence in the late 19th century, John D. Rockefeller controlled approximately 90% of the U.S. oil refining industry through his company, Standard Oil. This dominance allowed him to set prices and influence the market significantly, leading to widespread criticism and eventual antitrust actions against Standard Oil. His control over such a large portion of the oil business was unprecedented and played a crucial role in shaping the modern corporate landscape.