Some of America’s first urban workers lived in a unique type of Philadelphia home called a Trinity. Examples date from 1720. Trinities were built to house the artisan classes flocking to a burgeoning city; but while these workers moved on to populate America, the Trinity House didn’t follow them. But the Trinity and the narrow streets that contain them warrant a closer look.

A Trinity, as the name suggests, consists of three rooms stacked on top of each other – and that makes the whole house. A Betsy Ross stair punches through, basically an elongated spiral stair that is so narrow and steep that, instead of a railing for balance, you haul yourself up using a vertically mounted steel bracket.

via My Own Piece of Dirt | Metropolis POV | Metropolis Magazine.