During the period between 1870 and 1920, the gross national product of the United States increased more than sixfold, as revolutions in transportation, communications, and manufacturing sparked growth in the economy. Large industrial corporations emerged, and their growing power presented grave challenges for social policy, while their wealth enriched an unprecedented number of millionaires and multi-millionaires, whose contributions prompted an enormous increase in philanthropy across the nation. In particular, Andrew Carnegie sold his steel companies for $480,000,000 in 1901 and founded the Carnegie Institution of Washington in 1902, the Carnegie Foundation for the Advancement of Teaching in 1905, and the Carnegie Corporation of New York in 1911. Even more prominent, oil magnate John D. Rockefeller, “the most famous American of his day,” devoted $447,000,000 to endowing the Rockefeller Institute of Medical Research in 1901, the General Education Board in 1903, the Rockefeller Foundation in 1913, and the Laura Spelman Rockefeller Memorial in 1918.