By 1892, Standard Oil had a monopoly over all oil refineries in the United States. In an overall calculation of America's oil refineries' assets and capital, Standard Oil surpassed all. Standard Oil's combined assets equalled approximately $42,882,650 (equivalent to $ in ) in Indiana, Kentucky, New Jersey, New York and Ohio. Standard Oil also had the highest capitalization, totaling $26,000,000 (equivalent to $ in ). The history of American oil refining begins with Henry Morrison Flagler, and his business associate and friend, John D. Rockefeller, as they built the biggest, most prosperous and monopolizing oil empire of their time: Standard Oil.