The wealth gap hinges on how each man's fortune was calculated and what assets survived inflation adjustment. Rockefeller's $340M figure appears to be a snapshot of his liquid wealth or remaining holdings after Standard Oil's 1911 breakup, whereas Flagler's $1.9B represents the total value of his accumulated real estate, railroads, and infrastructure investments. Rockefeller's 90% oil monopoly generated massive annual cash flows ($90M+ yearly), but monopolies are inherently fragile—the Supreme Court dismantled Standard Oil and forced divestitures, fragmenting his wealth across multiple entities. Flagler, by contrast, bought undervalued swampland on Florida's east coast and physically transformed it into permanent, tangible assets: the Florida East Coast Railway, beachfront properties, hotels, and entire towns. Real estate appreciates and compounds; monopolies get litigated and split.