I spent three years living in Philadelphia for grad school and one of the things that I appreciated the most was its walkability. I walked and took transit everywhere. Much of this has to do with the grid system that was laid out for the city in the 17th century. But there are also lots of more recent developments that help to reinforce this fabric.

CityLab, for example, just published this article on Penn's Landing Square, which is a housing complex in Philadelphia's Society Hill neighborhood. Built in 1970 and designed by Canadian-American architect Louis Sauer, the modernist complex occupies an entire 2.37-acre block and contains an assortment of 118 low-rise homes, many of which are connected through small interior laneways.

Here's the site plan:

In addition to its handsome architecture, what is noteworthy about Penn's Landing Square is that its site plan makes it quite a dense low-rise development. At 118 homes, this translates into just under 50 units per acre. CityLab estimates that this means the development holds about 174 people per acre (~412 people total), which would make it more dense than Stuyvesant Town in New York (~158 persons per acre).

However, this is based on the assumption that there are almost 3.5 people living in each of these homes. While generally large, I don't know if this is the case. It would be higher than the average US household size. But regardless, from a unit per acre standpoint, it remains a great example of dense, family-oriented, and grade-related housing.

For fun, let's compare this to a more intense form of infill development. Our Junction House project, for instance, contains 151 homes and sits on a 0.48-acre piece of land. This translates into about 315 units per acre. I don't know off hand the average number of occupants per household, but I reckon that, given our larger average suite size, we should be on the higher end compared to most mid-rise condominiums. So I would say that we are probably 400+ people per acre.

It's unfair to compare a single development to an entire neighborhood, such as Stuyvesant Town. Circulation and other open spaces will necessarily pull down your average density. But these individual development examples do speak for themselves. There are many parts of North America where you might find 1 home or a handful of homes per acre of land. At Penn's Landing Square, this number is 50 units per acre. And at Junction House, it's 315 units per acre.