Jacob August Riis (May 3, 1849 – May 26, 1914), a Danish-American muckraker journalist, photographer, and social reformer, was born in Ribe, Denmark. He is known for his dedication to using his photographic and journalistic talents to help the less fortunate in New York City, which was the subject of most of his prolific writings and photographic essays. As one of the first photographers to use flash, he is considered a pioneer in photography.
Riis held various jobs before he landed a position as a police reporter in 1873 with the New York Evening Sun newspaper. In 1874, he joined the news bureau of the Brooklyn News. In 1877 he served as police reporter, this time for the New York Tribune. During these stints as a police reporter, Riis worked the most crime-ridden and impoverished slums of the city. Through his own experiences in the poor houses, and witnessing the conditions of the poor in the city slums, he decided to make a difference for those who had no voice.
He was one of the first Americans to use flash powder, allowing his documentation of New York City slums to penetrate the dark of night, and helping him capture the hardships faced by the poor and criminal along his police beats, especially on the notorious Mulberry Street. In 1889, Scribner's Magazine published Riis's photographic essay on city life, which Riis later expanded to create his magnum opus How the Other Half Lives. This work was directly responsible for convincing then-Commissioner of Police Theodore Roosevelt to close the police-run poor houses in which Riis suffered during his first months as an American. After reading it, Roosevelt was so deeply moved by Riis's sense of justice that he met Riis and befriended him for life, calling him "the best American I ever knew." Roosevelt himself coined the term "muckraking journalism", of which Riis is a recognized protagonist, in 1906.