Riis, Jacob August (rēs) [key], 1849–1914, Danish-American journalist, photographer, and social reformer, b. Denmark. He immigrated to the United States in 1870. In 1877 he became a police reporter for the New York Tribune and later for the New York Evening Sun. His reports on slum dwellings and the abuses of lower-class, largely immigrant life in New York City culminated in his first book, How the Other Half Lives (1890), a groundbreaking work of photojournalism, and earned him the admiration and friendship of Theodore Roosevelt. Riis founded a pioneer settlement house in New York (named for him in 1901). His association with the public park and playground movements was commemorated by the Jacob Riis Park on Long Island.
See his autobiography, The Making of an American (1901; new ed. with epilogue by his grandson, J. R. Owre, 1970); biography by L. Ware (1938); B. Yochelson and D. Czitrom, Rediscovering Jacob Riis (2008).