How the Other Half Lives: Studies Among the Tenements of New York (1890) was an early publication of photojournalism

Photojournalism

Photojournalism is a particular form of journalism that creates images in order to tell a news story. It is now usually understood to refer only to still images, but in some cases the term also refers to video used in broadcast journalism...

 by Jacob Riis

Jacob Riis

Jacob August Riis was a Danish American social reformer, "muckraking" journalist and social documentary photographer. He is known for using his photographic and journalistic talents to help the impoverished in New York City; those impoverished New Yorkers were the subject of most of his prolific...

, documenting squalid living conditions in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 slum

Slum

A slum, as defined by United Nations agency UN-HABITAT, is a run-down area of a city characterized by substandard housing and squalor and lacking in tenure security. According to the United Nations, the percentage of urban dwellers living in slums decreased from 47 percent to 37 percent in the...

s in the 1880s. It served as a basis for future "muckraking" journalism by exposing the slums to New York City’s upper and middle classes.
During the 1880s many people in upper- and middle-class society were unaware of the dangerous conditions in the slums among poor immigrants.