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.