Before the modern mortgage evolved, most people in colonial cities did not own their own homes (perhaps fewer than 10% of city dwellers at the time of the revolution). The greatest demand for rental housing was for small houses for the poor and working classes who couldn’t afford to even rent large houses, or afford the fuel to heat them. In the early 18th century, these houses were often made of wood (see the worker house behind the Todd house) but by the end of the 18th century and the early 19th century another typology had emerged – the trinity.
As its name suggests, the trinity consists of three single rooms, stacked one on top of another, and a basement for storage, and cooking. An enclosed spiral stair connected the floors. The cooking fireplace in the basement and a second fireplace on the ground floor could heat the whole house but heat could also be kept on the ground floor by closing a door on the winding stair.