Jacob August Riis (May 3, 1849 – May 26, 1914) was a Danish American journalist, photographer and reformer best known for How the Other Half Lives. Born the third of 15 children in Ribe, Denmark, he apprenticed as a carpenter and immigrated to the United States in 1870. He worked off and on as a carpenter in New York, Pittsburgh, Philadelphia and western New York State, and began to write. During this time he was frequently homeless and experienced poverty first hand. He returned to New York City and worked as a flatiron salesman before becoming editor of the weekly News and then police reporter for the New York Tribune, where he covered stories in the most impoverished and crime-ridden areas of the city. He was one of the first to use flash photography as means of vividly capturing the squalor of the slums, and developed a photographic archive consisting of pictures taken by him and his team along with those of other amateurs and professionals.  He gave lectures illustrated with slides that greatly increased the awareness of his subject and led to connections that, in turn, led to How the Other Half Lives, which sold well and made his reputation. In 1891 he exposed contamination in the New York City water supply, which led to life-saving improvements. He also worked with Theodore Roosevelt in 1895 in his efforts to reform the police in New York; later, President Roosevelt wrote a tribute that cited him as “the most useful citizen of New York”.