(1849–1914), U.S. social reformer, journalist, photojournalist, and author. Jacob Riis was known as the “Emancipator of the Slums” because he shocked the United States with his photographs of slum conditions. Born in Ribe, Denmark, Riis emigrated to the United States in 1870, where he became a police reporter in New York City. He was among the first photographers to use flash powder. He worked for reforms in tenement-house conditions. His photographs were published in ‘How the Other Half Lives' (1890). His autobiography, ‘The Making of an American', was published in 1901. (See also Photography.)