More important but less celebrated, Pierrepont then shifted his pitch to promise that the neighborhood character would be backed up by a legal guarantee. Only dwelling houses would be allowed — no rear-lot cooperages or blacksmith shops mixed in with residential uses. The homes had to be made of brick, with slate or metal roofs — no cheap, fire-prone, wood-frame, shingled-roof houses. They had to be actual (or aspiring) mansions — a minimum of 25 feet wide and two stories tall. All “to be set back 8 feet to form a straight line of fronts the whole length on each side of the streets.”
Source: Elections - nytimes.com