How Was Philadelphia Built

Penn's 1682 plan — a rectangular grid between two rivers with five public squares — was the first planned city in America and became the template for much of the country. Four of the five squares survive as parks, and the fifth holds City Hall.

The prevailing material is red brick. Philadelphia row houses, built in vast numbers through the eighteenth and nineteenth centuries, give whole neighbourhoods a uniformity that is the city's real architectural signature. Elfreth's Alley, begun in 1703, is the oldest continuously inhabited residential street in the country.

City Hall, finished in 1901, is the tallest load-bearing masonry building in the world, and a gentleman's agreement kept anything from rising above the William Penn statue on its tower until 1987 — which is why the skyline has an old low core and a sudden modern cluster.

The Benjamin Franklin Parkway, cut diagonally through the grid in the 1910s and 1920s, was modelled on the Champs-Élysées and strung with the city's museums.