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. The Panic of 1907 devastated several companies based in Pittsburgh, ending a period of strong growth. Some of Mellon's investments experienced a sustained down period after 1907, but most experienced a quick recovery. Mellon also became an investor in George Westinghouse's Westinghouse Electric Corporation after he helped prevent the company from going into bankruptcy. By the end of 1913, Mellon National Bank held more money in deposits than any other bank in Pittsburgh, and the Farmer's Deposit National Bank, which held the second-largest amount of deposits, was controlled by Mellon's Union Trust Company. In 1914, Mellon became a co-owner of Koppers, which produced a more sophisticated coking oven than the one that had earlier been pioneered by Frick. He also served as a director of various other companies, including the Pennsylvania Railroad and the American Locomotive Company. Mellon was deeply involved in the financing of World War I, as the Union Trust Company and other Mellon institutions provided millions of dollars in loans to the United Kingdom and France, and Mellon himself invested in Liberty bonds. In 1887, Frick, Andrew, and Richard Mellon jointly purchased Old Overholt, a whiskey distillery located in West Overton, Pennsylvania.