When American railroad promoters, in the years immediately after 1830, had to look beyond their own regions for capital, they turned first to Broad Street in Philadelphia, where Nicholas Biddle and his associates served as the agents for marketing vast amounts of sterling bonds in London. This mechanism was disrupted by the failure of the Bank of the United States of Pennsylvania in 1841. Then State Street in Boston became the center, and common stock became the chief instrument, of American railroad finance. The sharp recession of 1847 showed that the Boston capitalists had already made long-term investments in excess of the liquid capital available to them. New York merchants, bankers, and brokers now took up the task of financing the railroads of the South and West, and Wall Street became the undisputed financial center of the country.