Hydroelectric power stations continued to become larger throughout the 20th century. Hydropower was referred to as "white coal". Hoover Dam's initial power station was the world's largest hydroelectric power station in 1936; it was eclipsed by the Grand Coulee Dam in 1942. The Itaipu Dam opened in 1984 in South America as the largest, producing , but was surpassed in 2008 by the Three Gorges Dam in China at . Hydroelectricity would eventually supply some countries, including Norway, Democratic Republic of the Congo, Paraguay and Brazil, with over 85% of their electricity. The United States currently has over 2,000 hydroelectric power stations that supply 6.4% of its total electrical production output, which is 49% of its renewable electricity.