Jacob Riis was a Danish-born journalist and photographer who became a prominent social reformer in the United States during the late 19th and early 20th centuries. After emigrating from Denmark in 1870, he experienced extreme poverty in New York City, which later informed his investigative work. By documenting the squalid living conditions of the urban poor through photography and writing, he sought to inspire the middle and upper classes to support housing reforms and improve the lives of those living in crowded tenements.