William Rockefeller, 1841–1922, American financier, b. Tioga co., N.Y.; brother of John D. Rockefeller. He joined (1865) his brother in the oil-refining business. William was a successful stock market manipulator and was the New York representative of the Rockefeller interests until the Standard Oil Company of New Jersey was dissolved (1911) by the Supreme Court. He was associated with copper interests, railways, and public-utility corporations. With his vast resources he built up the National City Bank of New York.