Using this invention, he was able to photograph low-light scenes. He was able to capture the plight of the poor and bring to light the hardships they faced every day. He began displaying his work as lantern slides as part of lectures presented as entertainment, however, he also published his work in a book titled How the Other Half Lives. The book was published in 1890 and became an international phenomenon. His writings, along with his photographs, forcefully affirmed society's indifference towards the poor. As an advocate for the poor, oppressed, and exploited, Riis wrote how they were victims of economic slavery. His writing caused shock and horror among New York's middle and upper classes. It also caught the attention of Theodore Roosevelt. After Roosevelt became governor, he closed the almshouses and implemented many reforms that helped fight poverty in the slums. Roosevelt called Riis the “most useful citizen in New