Because of his extensive study of European public and private financing systems during 1901, Vanderlip helped National City Bank become a tremendous resource for American businesses wishing to expand abroad. Vanderlip’s international interest led to the building of the first foreign branch of any United States bank, National City’s branch in Buenos Aires, and to the creation of the banking conglomerate American International Corporation, which had operations in 17 countries by 1918. Because of Vanderlip’s leadership, National City grew to be the largest bank in the United States.