How Philly Got Flat: Piling it on at the Logan Triangle

1895: Detail of Wingohocking Creek and the projected street grid from the G. W. Bromley Philadelphia Atlas. (Philadelphia GeoHistory Network)

Rolling Hills? Maybe once upon a time. But at the dawn of the 20th century, when the City of Homes meant rowhouses, as far as the eye could see, Philadelphia had to be flator as close to flat as humanly possibleif it was to have any value on the real estate market.

And so, one by one, Nature’s dips, rises and rolls were raised up or shaved down as the city grid marched north. Once flattened, Philly invited horse drawn streetcars on its newly leveled streets, which meant developers and then new residents. Mile by mile, that’s how the city boomed to more than double its population between the Civil War and 1900.

1903: Taking the Wingohocking underground. Sewer Construction at 7th and Courtland Streets. Detail. (

As mid-century became turn-of-the-century,Broad Street forged northward past Ridge Avenue to Monument Cemetery (Temple University, today). It then trundled over the bridge at Cohocksink Creek (soon to become Dauphin Street), over Gunners Run (just south of the would-be Allegheny Avenue) and past Hunting Park, where a race-course-turned-public-park sprawled to the east. Now, little more than a wide lane, Broad Street approached the largest creek so farthe Wingohocking. And as it flowed eastward to join Frankford Creek, the Wingohocking did what creeks do: it meandered a bit to the north, and then a bit to the south, crossing where Courtland Street was supposed to be, no less than four times from Broad to 6th.

What’s to be done when the dips are gullies are actually valleys surrounded by rolling hills? Philly’s flatlanders had a ready-made solution. Run the creeks through giant culverts: massive, man-made, underground masonry aqueducts large enough to allow Mother Nature to carry on unimpeded—out of sight— and possibly out of mind. And even more convenient: these hidden, creek beds could double as the city’s backup sewer system, on an as-needed basis, when the occasional flood strikes. Above, on the level, it’s business as usual.Or that was the idea.

So they channeled the Wingahocking where it meandered. And over it, and over anything that laid lower than the idea grade for Philadelphia, well, that, too, would be covered with a deep layer of fill. Ambitious? To be sure. But doable.

2000: Detail of Map Showing the Distribution of Fill in the Frankford and Germantown Quadrangles (U.S. Department of the Interior / U.S. Geological Survey) Click image for original map (7.2MB PDF).

By the 1880s, historians Scharf and Westcott had seen it happen, again and again. “There have been great changes in the face of [Philadelphia], in its levels and contour, and in the direction and beds of its water-courses… Some streams have disappeared, some have changed their direction, nearly all have been reduced in volume and depth…in the building of a great city.” Scharf and Wescott had seen a lot, but nothing like was about to happen along the Wingohocking. As water historian Adam Levine tells it: “In some watersheds, it took many years to completely obliterate the main stream and its tributaries.” West Philadelphia’s conversion from Mill Creek to sewer “took more than 25 years, and the city’s largest such project, the burying of both branches of Wingohocking Creek, took about 40 years.” Raising the 80-acre Winghocking valley up to city grid grade would require as much as 40 feet of fill.

Aside from urban esthetics and environmental ethics, this massive project had every reason to work—if only the contractors had used rock and soil for fill. But, in one of Philadelphia’s most egregious and purposeful bungles, the fill hauled in by specially-designed streetcars was ash and cinder, an estimated 500,000 cubic yards of it. In time, the consequences would be as dire as the hauling and dumping project had been efficient. “It took decades for the inadequacy of the ash to be revealed,” writes Levine. But when the fill washed away, gas lines ruptured and the neighborhood above found itself in the midst of “an epidemic…of sagging porches, cracking foundations” and worse, much worse.

The saga of Philadelphia’s Logan Triangle had begun.