As far back as the mid-1940s, the journalist John Gunther wrote in Inside U.S.A. (1947) that "Philadelphia retains some remarkable atavisms." The city's glassed-in air was stifling, but it seemed to slow the process of decay. Thus in writer Nathaniel Burt's time, and still today, half a century later, "quaint" survivors from an earlier age endure: a patinated parallel universe of social clubs, rowing clubs, singing societies, drama clubs, military troops, workshops, and athletic associations. This is our good fortune. These institutions deepen and enrich our urban experience by drawing the past into the present. Members of the Racquet Club, still among the economic and social elite, play two archaic sports, court tennis and racquets.

In this way Philadelphia became, in the late 20th century, a place of remarkable contrasts. Astounding levels of poverty and dissolution surrounded some of these clubs, factories, and churches; other clubs, factories, and churches merely went on, cheek by jowl with the working-class masses. Either way, their legacy owners, members, and worshipers did not advertise their presence; indeed, in many cases they took pains to conceal it. For those not directly concerned with them, which is to say almost everyone, their existence was largely unknown, unsought, and, even when physically seen, unrecognized, because no one suspected (or even dreamed) what might be inside their walls.

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The remains of the long 19th century — with its emphasis on materials, its alluring buildings, and its looms, libraries, furnishings, lathes, turbines, boilers, spools, and pumps — beg to be seen. Present-day Philadelphians, with an eagerness to discover and engage, have inherited hundreds of architecturally impressive mills and factories, schools, theaters, churches, and civic buildings, some restored, others abandoned or underutilized, prizes of Philadelphia's postindustrial inertia.

A city of accretion, Philadelphia is not a dynamic city, in the manner of New York, nor a collapsed city, like Detroit, nor a city where much of the past has been polished like a family heirloom, like Boston or Charleston. Rather, Philadelphia embodies some elements of each. Like New York, Philadelphia takes its energy from immigrants and economic innovation and a brisk East Coast pace. Like Detroit, Philadelphia has experienced an industrial collapse that emptied factories and mills and produced seemingly intractable racialized poverty. Like Boston and Charleston, Philadelphia has taken special care to preserve landmarks and streetscapes of a definitive historical period, while leaving the bulk of the city, built in the long 19th century, without legal protection.

Keeping its layers hidden in the accretive cityscape, Philadelphia itself is hidden, sandwiched between New York and Washington, and removed from the contemporary narrative of the United States. And yet, until about 1925 — when its financiers could no longer keep up with New York's and its provincial political machine stopped producing leaders of national ambition — it was central to that narrative. Philadelphia's cultural zeitgeist is (usually, though not always) prone to reticence; it hides its wealth and guards its influence. The many lives of the city are hidden down narrow streets and alleys and behind the brick façades of rowhouses, one barely distinguishable from the next. For these reasons Philadelphia is naturally, and characteristically, the Hidden City.

In our book we invite readers to seek the Hidden City. We argue that the act brings them into direct contact not only with the city that is, but the city that was. The layers are the product of the past, of others' ideas and adaptations. From a material standpoint we can see and touch what others, long before us, have done and made. This encounter interrupts the dominant progressive nature of time, the incessant forward motion of contemporary life. It begs us to think of the latent past as a kind of frontier for exploration. In Philadelphia, even more than in other American cities, this frontier is, to those who know how to look, at once an unmarked victim of neglect, a legible tableau of urban history, and the raw material of the future.

Excerpted from:"Philadelphia: Finding the Hidden City" by Joseph E. B. Elliott, Nathaniel Popkin, and Peter Woodall.  Temple University Press