As the United States industrialized during the 19th century, immigrants and workers from the countryside were housed in former middle-class houses and other buildings, such as warehouses, which were bought up and divided into small dwellings,^[6][7] and also, beginning as early as the 1830s in New York City‘s Lower East Side^[4] or possibly the 1820s on Mott Street,^[8] in jerry-built 3- and 4-floor “railroad flats” (so called because the rooms are linked together like a train)^[9] with windowless internal rooms. The adapted buildings were also known as “rookeries,” and were a particular concern as they were prone to collapse and fire. Mulberry Bend and Five Points were the sites of notorious rookeries that the city worked for decades to clear.^[8] In both rookeries and purpose-built tenements, communal water taps and water closets (either privies or “school sinks,” which opened into a vault that often became clogged) were squeezed into what open space there was between buildings.^[9] In parts of the Lower East Side, buildings were older and had courtyards, generally occupied by machine shops, stables, and other businesses.^[10]

Lower East Side Tenement Buildings

Such tenements (or “walk-ups”) were particularly prevalent in New York, where in 1865 a report stated that 500,000 people lived in unhealthy tenements, whereas in Boston in 1845 less than a quarter of workers were housed in tenements.^[4] One reason New York had so many tenements was the large numbers of immigrants; another was that the grid pattern on which streets were laid out and the economic practice of building on individual 25- by 100-foot lots combined to produce extremely high land coverage, including back building.^[11] Prior to the 1867 law, tenements often covered more than 90 percent of the lot, were five or six stories high, and had 18 rooms per floor of which only two received direct sunlight. Yards were a few feet wide and filled with privies where they had not been entirely eliminated. Interior rooms were unventilated.^[9]

model of a lower east side tenement block ca 1900: click to enlarge

Early in the 19th century, many of the poor were housed in cellars, which became even less sanitary after the Croton Aqueduct brought running water to wealthier New Yorkers: the reduction in well use caused the water table to rise, and the cellar dwellings flooded. Early housing reformers urged the construction of tenements to replace cellars, and beginning in 1859 the number of people living in cellars began to decline.^[12]

The Tenement House Act of 1867, the state legislature’s first comprehensive legislation on housing conditions, prohibited cellar apartments unless the ceiling was one foot above street level; required one water closet per 20 residents and the provision of fire escapes; and paid some attention to space between buildings.^[13] This was amended by the Tenement House Act of 1879, known as the Old Law, which required lot coverage of no more than 65 percent. The New York City Board of Health, empowered to enforce the regulations, declined to do so. As a compromise, the Old Law tenement became the standard: this had a “dumbbell” shape, with air and light shafts on either side in the center (usually fitted to the shafts in the adjacent buildings), and typically covered 80 percent of the lot.^[14] James Ware is credited with the design;^[15] he had won a contest the previous year held by Plumber and Sanitary Engineer magazine to find the most practical improved tenement design, in which profitability was the most important factor to the jury.^[16]

Public concern about New York tenements was stirred by the publication in 1890 of Jacob Riis‘ How the Other Half Lives.^[17] The New York State Assembly Tenement House Committee report of 1894 surveyed 8,000 buildings with approximately 255,000 residents and found New York to be the most densely populated city in the world, at an average of 143 people per acre, with part of the Lower East Side having 800 residents per acre, denser than Bombay. It used both charts and photographs, the first such official use of photographs.^[18] Together with the publication in 1895 by the U.S. Department of Labor of a special report on housing conditions and solutions elsewhere in the world, The Housing of Working People, it ultimately led to the passage of the Tenement House Act of 1901, known as the New Law, which implemented the Tenement House Committee’s recommendation of a maximum of 70 percent lot coverage and mandated strict enforcement, specified a minimum of 12 feet for a rear yard and 6 feet for an air and light shaft at the lot line or 12 feet in the middle of the building (all of these being increased for taller buildings), and required running water and water closets in every apartment and a window in every room. There were also fire-safety requirements. These rules are still the basis of New York City law on low-rise buildings, and made single-lot development uneconomical.^[19]

Most of the purpose-built tenements in New York were not slums, although they were not pleasant to be inside, especially in hot weather, so people congregated outside, made heavy use of the fire escapes, and slept in summer on fire escapes, roofs, and sidewalks.^[20]

The Lower East Side Tenement Museum, a five-story brick former tenement building in Manhattan that is a National Historic Site, is a museum devoted to tenements in the Lower East Side.