* Riis's most famous work was his book How the Other Half Lives, published in 1890, which exposed the squalid conditions in which many immigrants and working-class people lived in New York City. The book was an important influence on the development of the Progressive Era, a period of social and political reform in the United States in the late 19th and early 20th centuries.
* Riis's photographs of the slums of New York City, some of which were published in How the Other Half Lives, were also influential in raising public awareness of the plight of the poor.
* Riis's work also helped to inspire the creation of social welfare programs, such as the Tenement House Act of 1895 and the Child Labor Act of 1916, which were designed to improve the lives of the urban poor.
In addition to his work as a muckraker, Riis was also a reformer and an advocate for the poor. He helped to found the Children's Aid Society, an organization that provided services to poor children, and he also served as a member of the New York State Tenement House Commission, which was established to investigate the living conditions of the urban poor.