In 1902, Mellon reorganized T. Mellon & Sons as the Mellon National Bank, a federally chartered National Bank. Andrew Mellon, Richard Mellon, and Frick drew up a new business arrangement in which the three of them jointly controlled the Union Trust Company, which in turn controlled Mellon National Bank. They also established Union Savings Bank, which accepted deposits by mail, and the Mellon banks flourished in the first years of the 20th century. While Mellon's financial empire prospered, his investments in other areas, including Pittsburgh's streetcar network, the Union Steel Company (which was bought out by U.S. Steel), and the Carborundum Company, also paid off handsomely. Another successful Mellon investment, the Standard Steel Car Company, was created in partnership with three former U.S. Steel executives. As part of the Texas oil boom, the Mellons also helped J. M. Guffey establish the Guffey Company. The Mellons later removed Guffey as the head of his company, and in 1907 they reorganized the Guffey Company as Gulf Oil and installed William Larimer Mellon Sr. (a son of Andrew Mellon's older brother, James Ross Mellon) as the head of Gulf Oil. The success of Mellon's financial empire and his varied investments made him, according to biographer David Cannadine, the "single most significant individual in the economic life and progress of western Pennsylvania" in the first decade of the 20th century.