The photographs served as a basis for future "muckraking" journalism by exposing the slums to New York City's upper and middle classes.
This migration was vastly different from the previous booms due to the influx of non-western European and non-Protestant individuals, which made the split between the "new" and "old" immigrants much larger.
[9] When the Tenement House Act of 1867 was passed, the tenement was defined as: Any house, building, or portion thereof, which is rented, leased, let or hired out to be occupied or is occupied, as the home or residence of more than three families living independently of one another and doing their own cooking upon the premises, or by more than two families upon a floor, so living and cooking and having a common right in the halls, stairways, yards, water-closets, or privies, or some of them.
[16] In January 1888, Riis bought a detective camera and went on an expedition to gather images of what life was like in the slums of New York City.
The book version of Riis' work was published in January 1890 as How the Other Half Lives: Studies among the Tenements of New York.
Riis describes a system of tenement housing that had failed, as he claims, because of greed and neglect from wealthier people.
He claims a correlation between the high crime rate, drunkenness, and reckless behavior of the poor and their lack of a proper home.
[23] While Riis treats many of the ethnic groups he encounters with slurs and numerous stereotypes, he still keeps his general hypothesis that the reason for the poverty in these communities is caused by the conditions surrounding them.
[26] How the Other Half Lives follows a general outline for the charity writings of the nineteenth century: a section on crime, the Protestant virtues and vices (intemperance, idleness, disorder, uncleanliness), miserable conditions of living, disease, the loss of modesty (especially women), the dissolution of the family, the institutions that would help in their uplift, as well as future sources of reform.
[27] The difference introduced photography to prove the squalid conditions and to increase sympathy for the individuals living in these slums.
Riis finally convinced the average reader of newspapers that the poor were not so by choice; that the dangerous and unhygienic conditions in which they lived were imposed by society, rather than the result of loose moral standards; that the slums were something that needed to be fixed rather than gaped at or shunned.
[29] The Christian Intelligencer reviewed the first edition saying "Books like this that lift the curtains and expose to public gaze the great evils of the system will hasten the day of reform.
[33] Because of this awakening caused by Riis' efforts, many reforms were quickly compiled to improve conditions for the working poor.
[34] In addition to this legislature, more reform was brought about by the New York Tenement House Act of 1901, which changed the minimum requirements of tenement housing to include reforms in the amount of light received by living quarters, increased fire safety regulations, more ventilation, restrictions on building height, and increased room space.