A typical tenement building had five to seven stories and occupied nearly all of the lot upon which it was built, usually 25 feet wide and 100 feet long, according to existing city regulations. Many tenements began as single family dwellings, and many older structures were converted into tenements by adding floors on top or by building more space in rear-yard areas.

With less than a foot of space between buildings, little air and light could get in.

In many tenements, only the rooms on the street got any light, and the interior rooms had no ventilation, unless air shafts were built directly into the room. Later, speculators began building new tenements, often using cheap materials and construction shortcuts. Even new, this kind of housing was at best uncomfortable and at worst highly unsafe.

In the 19th century, more and more people began crowding into America’s cities, including thousands of newly arrived immigrants seeking a better life than the one they had left behind. In New York City, where the population doubled every decade from 1800 to 1880, buildings that had once been single family dwellings were increasingly divided into multiple living spaces to accommodate this growing population.

Known as tenements, these narrow, low rise apartment buildings, many of them concentrated in the city’s Lower East Side neighborhood, were all too often cramped, poorly lit and lacked indoor plumbing and proper ventilation. By 1900, some 2 point 3 million people, a full two thirds of New York City’s population, were living in tenement housing.

In the first half of the 19th century, many of the more affluent residents of New York’s Lower East Side neighborhood began to move further north, leaving their low rise masonry row houses behind. At the same time, more and more immigrants began to flow into the city, many of them fleeing the Irish Potato Famine, or Great Hunger, in Ireland or revolution in Germany. Both of these groups of new arrivals concentrated themselves on the Lower East Side, moving into row houses that had been converted from single family dwellings into multiple apartment tenements, or into new tenement housing built specifically for that purpose.

Two major studies of tenements were completed in the 1890s, and in 1901 city officials passed the Tenement House Law, which effectively outlawed the construction of new tenements on 25 foot lots and mandated improved sanitary conditions, fire escapes and access to light. Under the new law, which in contrast to past legislation would actually be enforced pre existing tenement structures were updated, and more than 200,000 new apartments were built over the next 15 years, supervised by city authorities.