When I visited Philadelphia in April 2007, I stayed with my friend Emily in an improbably tiny house. She had explained that it was off a pedestrian alley off an alley – itself an unusual description – but when I entered I discovered the house had, apparently, just one room.

A tiny, twisting staircase led up one floor to another tiny room and bathroom, and the staircase led up again to a bedroom. Instead of conveying claustrophobia, the house exuded a comfortable, almost nautical sensation of functional smallness. The style was known as a “trinity house,” Emily explained, a uniquely Philadelphia invention. My interest piqued, I turned to the web and library for more information on these unique structures. My search eventually led to one of the city’s most famous residents, Benjamin Franklin, and offered a window into the city’s early history. Many trinity houses turned up for sale or rent on Craigslist, often along with photos of their interiors. A discussion forum operated by a local blog describes residents moving beds in through second story windows, and the unique quirks of living in such small homes.

Few websites could describe their origins, number, or typical form. One real estate website described the type as some of the city’s oldest houses, generally over 100 years old, cozy, and located off shared courtyards. A Frommer’s webpage describing the architecture one might encounter during a walking tour provides just one short sentence, contrasting them with their larger neighbors, “The less wealthy lived in ‘trinity’ houses — one room on each of three floors, named for faith, hope, and charity.” However, other sources contradicted the name’s origin. The introduction to a collection of stories about the 19th century working class neighborhood Flatiron reports residents of the Catholic section called their 14-foot-wide homes “Father, Son and Holy Ghost houses” for their three-room makeup.(1)

Early examples of the buildings dating from the 18th century have been preserved in a National Historic Landmark called Elfreth’s Alley. A nonprofit educational organization sponsors tours of the alley and boast it’s the oldest continuously inhabited neighborhood in America. While the official website doesn’t use the term, another unofficial website describes the architecture as Georgian and “trinity.”

A 1986 Philadelphia Magazine article by Stephen Fried points out the homes are precisely what city founder William Penn hoped to avoid when he founded a city he envisioned would be a “greene Country Towne” filled with homes set amid gardens. The article describes the homes usual form, reporting they are “much in demand” among the well-to-do, and that sometimes several are combined to form “quadities” or “quantities.” For an example of the form, the author suggests Elfreth’s Alley, or the 1900 block of Waverly Street. The author also describes a typical layout: a kitchen in the basement, and the homes often had two front entrances, one leading up to the living room and another providing access to the basement.(2)

An essay on housing for the poor provides additional insight into the origin and early history of the homes. The author describes how property speculators built long rows of identical row homes, and even how the city took possession of small alleyways and subdivided them. The process of what he calls back-alley dwellings is described:

The back-alley dwellings represented a particularly difficult problem. They took several forms. Owners of houses fronting on main streets might simply add on buildings in the rear to the end of the lot, creating a dark, unpaved, unsewered alley. A more famous Philadelphia rear-dwelling was the band-box, or “father, son, holy ghost” house. These houses rarely fronted the streets, but instead were built in the back yards and formed little courts, which were often invisible from the street. Of three, or less frequently two, stories, they contained only one room per floor, with an unenclosed stairway leading from one floor to another. They could be suitable for one small family, but they were unfit for the poor who often crowded into them. These real courts multiplied as the city’s original large lots were subdivided. They were probably built both for speculation and for servants’ quarters. Of great significance is the fact that they were rear dwellings, often obscured from the view of passers-by.(3)

This description is accompanied in the text by a diagram from W. E. B. DuBois’s text The Philadelphia Negro. However, a simple aerial photograph of the trinities above can illustrate the ingenuity of Philadelphia’s alley developers:

Sutherland describes how these houses afford home ownership to the city’s ethnic communities and avoid the problems of high-density tenements like in New York. However, the overcrowding and substandard sanitation caused high rates of typhoid and tuberculosis. His analysis of tenant owners reveals they generally did not hold extensive properties, and often lived in the building itself or nearby.

Sam Bass Warner’s classic account of Philadelphia’s growth suggests one of the city’s most famous residents was responsible for several trinity homes.

To accommodate as many families in so little space some of the blocks for the ward had been cut by alleys so that little houses might be crowded onto the back lots of the houses facing the main streets. Strawberry Alley and Elbow Lane cut through the first block, Petty’s alley divided the third block, and Benjamin Franklin had begun the alley process with his house lot off Market Street in the second block of the ward. He had built a row of three houses on Market Street, thereby turning his home yard into an interior lot. … In the early nineteenth century Franklin’s home parcel became Franklin Court, an alley lot which opened up the interior of the block.(4)

Warner reports the tremendous density and low sanitation caused periodic epidemics of yellow fever, typhoid, small pox, and dysentery. He finds the 1774 census reported 1,401 people and 337 dwellings in the city’s middle ward, composed in turn of five developed block of “slightly less than five acres of land.” Erring on the generous side to assume the ward was composed of 25 acres of developed land would yield the density of 13.5 dwelling units per acre (more than 55 people per acre), considered a high density today, let alone in an era without modern sanitation. He reports that street railways opened up “cast tracts of cheap suburban land and thereby destroyed the market for new alley construction.” Noting many of the old alleys remained standing for years “giving discomfort to Philadelphia’s poor for many generations.”

It is no small irony that the extremely dense urban fabric that constituted an urban problem in the 18th century is precisely the antidote to 21st century ones: sprawl, housing un-affordability, and auto dependence. Now may be the right time to learn from Philadelphia’s trinities, to study their dimensions and construction, as we seek to learn how to build more humane, resource-efficient urban homes and neighborhoods.

> See also my post on “An Architectural Aesthetic of Efficiency,” about how the “forced austerity” of the third world can result in a fundamental re-evaluation of residential architecture

(1) Gerard, Shields. Flatiron. Hilliard & Harris Publishers: 2006.
(2) Fried, Stephen. Philadelphia Magazine. April 1986. “The Trinity House – Last Thing Founding Father Thought He’d Be Remembered For.”
(3) Sutherland, John F. “Housing for the Poor in the City of Homes: Philadelphia at the Turn of the Century.” Chapter 9 in The Peoples of Philadelphia: A History of Ethnic Groups and Lower-Class Life, 1790-1940. Allen F. Davis and Mark H. Haller, eds. Philadelphia: Philadelphia University Press, 1998.