Wild Philly

Explore the Amazing Nature in and Around Philadelphia


By Mike Weilbacher

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A vibrant, family-friendly guide to the unexpected nature found in and around Philadelphia.

Philadelphia may seem like a concrete jungle, but in reality, it's full of amazing wildlife. You just need to know where to find it!  Equal parts natural history, field guide, and trip planner, Wild Philly has something for everyone. This handy yet extensive guide looks at the factors that shape local nature and profiles over 100 local species, from beautiful flowers and towering trees to majestic birds and surprising city-dwellers like coyotes and red foxes. Also included are descriptions of day trips that help you explore natural wonders on hiking trails, in public parks, and in your own backyard. 



Our “Greene Country Towne”

Philadelphia is a city of American firsts: the nation’s first hospital, public school, volunteer fire department, printed treatise against slavery, paper mill, and asylum for treating mental illness. The Swedes built America’s first log cabins along the Delaware River in the early seventeenth century, and the city’s Quakers later built America’s first brick houses. A hotbed of natural history and science, Philadelphia is also the home of America’s first natural history museum, botanical garden, zoo, and science institution, the American Philosophical Society.

We’re also America’s first planned city, the first and only one designed by Quakers. Anchored by the five public squares that are America’s first parks, Philly was designed by surveyor Thomas Holme and William Penn himself, whom architecture critic Inga Saffron notes “was, at his core, a real estate developer—among America’s first.”

But why is Philadelphia located where it is? How did nature fit into Penn’s plans, and what was the land like when Penn first sailed up the Delaware on the Welcome in October 1682?

Though the land was inhabited by the Lenape for millennia, the colony that would be called Pennsylvania was founded a year earlier, in 1681, when King Charles II gave William Penn a charter for more than 45,000 square miles of land in the New World, settling the king’s debts to his father, Sir Admiral William Penn. Wanting a holy experiment where Friends (as the Quakers are known) and others could practice religious freedom—also an American first—Penn originally christened his new holdings Sylvania after its forests. It was King Charles who renamed it Pennsylvania, Penn’s Woods, in honor of the elder Penn.

“Always Be Wholesome”

When he founded Philadelphia, William Penn wrote as a key organizing principle for the city that it would be a “greene Country Towne which will never be burnt and always be wholesome.” It was less that Penn was a nature-loving visionary with a grand notion of open space and more that he was a smart and surprisingly practical man reacting to two seminal events from his native London: the Great Plague of 1665 and the Great Fire only one year later. The former killed perhaps 100,000 Londoners, some 7600 in its first week alone, and the latter swept through the wooden city, burning more than 400 acres, more than 13,000 homes, and 87 of the city’s 109 churches. Then a young man in his twenties, these events would have been seared in Penn’s memory.

A map of “Pensilvania” in 1690, by British cartographer John Seller. By then, there were already many European place names along the Delaware (Philadelphia, Chester, New Castle), but a strong presence of Native American place names along the Susquehanna River and in “West New Iarsey.” Note the spelling of “Skoole Kill” River.

For Penn, Philadelphia was a chance to right London’s wrongs. One significant change from London was that in Philadelphia homes would be spaced far apart on wide boulevards. He was practicing a seventeenth-century form of social distancing to combat both fire and plague. He also advocated for wide lots “so there may be ground on each side for Gardens or Orchards, or feilds [sic].”

In 1681, Penn sent a team of commissioners across the Atlantic to seek out a site for his planned city and negotiate purchases with the Lenape and other settlers. He told his team that the river had to be navigable, and the bank needed to be “high, dry and healthy,” not a marshy lowland that would breed diseases like malaria (literally “bad air”). Equally important, low-lying sites would prove difficult moorage for ships that needed to load and unload both cargo and immigrants for the city. It should also be open land free of other inhabitants, and if people were living there, perhaps they would agree to trade for land elsewhere.

William Penn’s arrival in Philadelphia in 1682, as depicted by William L. Bretton in 1833. Penn stands in the center of a smaller boat, as his Welcome remained anchored in today’s Chester. Note even then the presence of an inn where Dock Creek meets the Delaware River and the watchful Lenape in the foreground.

But when the commissioners arrived and began scouting the new territory, they did not find unsettled land along the river. In fact, Swedes and Finns had been inhabiting what they called New Swedeland for 50 years already. The commissioners’ first choice was a settlement called Upland, at the site of today’s Chester, but they were unable to purchase that site.

So the commissioners moved upriver, where they found a few hundred farmers, trappers, and traders strung out along both the Delaware and Schuylkill Rivers, the settlements then extending along the Delaware as far as today’s Trenton. Among the most attractive sites (spoiler alert) was the narrow neck of land at the junction of the Delaware and the Schuylkill. The rivers were both navigable, at least for small vessels; “the bank was bold and high,” said an 1851 biography of Penn, “the air pure and wholesome, the neighboring lands were free from swamp, clay for making into brick was found on the spot, and immense quarries of good stone abounded within a few miles.”

The commissioners first purchased 300 riverside acres from the Swedish Swanson brothers in today’s Queen Village, where the now-filled Hollander Creek once emptied into the Delaware. Near today’s Gloria Dei Church, the Swansons called this site Wicaco, the Lenape name for their former settlement there, an anglicized and shortened corruption of a Lenape phrase roughly meaning “the place of pine trees at the head of a creek.” This history is captured by the church’s address on Swanson Street. Other Swedes ultimately sold (the Swedes pointedly say “surrendered”) some 1200 acres for the new city. While not the 10,000 acres Penn originally hoped for, it was a start.

“A Lush American Eden”

“While Penn envisioned Philadelphia as a lush American Eden,” wrote Inga Saffron, he also “recognized that the inclusion of open space could help make his urban experiment more appealing to buyers.” So with his surveyor Thomas Holme, Penn laid out the city with High Street running between and connecting the two rivers and Broad Street dividing the city vertically. Both streets were more than 100 feet wide, wider than any London boulevard at the time.

With the city in four quadrants, they designed the now-iconic five town squares, one in each quadrant with a fifth in the middle where Broad meets High. Penn had envisioned the city’s public buildings lining the center square and facing it, which did not happen.

While the new city’s gridded river-to-river map was widely circulated, new settlers had other ideas. “Early development,” notes architecture critic and Philadelphia writer Michael J. Lewis, “huddled with near-medieval intensity along the Delaware River, where the city’s economic life was based.” They were not spreading out as Penn hoped. Tour guide and author Jim Murphy adds that settlers “developed their own system of alleys or cartways,” like the frequently visited Elfreth’s Alley, America’s oldest intact street. “By 1698,” Murphy added, “nine lanes ran from Front to Second Street, thwarting Penn’s plan and violating his dream of a green country town.”

William Penn’s iconic layout of the new city, with five squares and generous avenues.

An intriguing 1702 aerial sketch of the growing city shows, among many things, “caves” along the Delaware, an “Indian camp” in South Philly, and Dock Creek, a stream flowing from a “Duck Pond” into the Delaware below Walnut Street. Dock Creek later became a pollution concern for Ben Franklin.

In 1698, more than 15 years into this holy experiment, a young British Quaker named Gabriel Thomas offered in his “Account of the Country of Pensilvania” this assessment of the new city: “Since [its founding], the industrious inhabitants have built a noble and beautiful city . . . which contains above two thousand houses, all inhabited; and mostly stately, and of brick generally three stories high.” Commenting further, Thomas seems to sarcastically poke at two professions. “Of Lawyers and Physicians, I shall say nothing,” he wrote, “because this countrey [sic] is very peaceable and Healthy; long may it so continue and never have occasion for the Tongue of the one nor the pen of the other, both equally destructive of Men’s Estates and Lives.” Even then the Philadelphia lawyer was famous.

By 1700, more than 5000 people called Philadelphia home, and the city continued growing, with 13,000 residents in 1740 and 28,500 in 1790. By the end of that century, Philadelphia was not only the American capital, but the most populous city in the new country and the second largest city in the English-speaking world after London.

“Few Rivers of America Have More”

In his ship’s log of 1634, British Captain Thomas Yong wrote that the Delaware “aboundeth with beavers, otters, and other meaner furs. . . . I think few rivers of America have more . . . the quantity of fowle [sic] is so great as hardly can be believed. Of fish here is plenty, but especially sturgeon.” Penn himself noted the sturgeon. When he first sailed up the Delaware in 1682, he wrote of 6-inch oysters in the river “too big to be eaten whole” and large sturgeon that “played in the river all summer.”

A 1777 map of Philadelphia beautifully rendered for the British shows the city still hugging the river, with Passyunk and Moyamensing as separate townships. Note the network of islands where the Delaware and Schuylkill meet, which have since been filled in, and the hills around the “Faire Mount,” the area of the Philadelphia Museum of Art.

Writing to the Earl of Arran in 1684, Penn described the animal life of his territory, in the curious archaic spelling of that era: “the food the woods yeild is your Elk, deer, Raccoons, Beaver, Rabbets, Turkey, Phesants, heathbirds [quail?], Pigeons [passenger pigeons] & Partridge [grouse?] innumerably . . . of foul the swan, white & gray & black goose and brands [brants], the best teal I ever eate and the Snipe & curloe [curlew] with the Snow bird are also excellent.”

In the same vein, Penn wrote back to England that “the trees of most note are the black walnut, cedar, cypress, chestnut, poplar, gumwood [sweet gum], hickory, sassafras, ash, beech, and oak of divers [sic] sorts, as red, white, and black, Spanish, chestnut, and swamp, the most durable of all; of all of which there is plenty for the use of man.” After cataloging the trees, he noted the abundant fruits available for eating: “The fruits that I find in the woods are the white and red mulberry, chestnuts, walnut, plums, strawberries, cranberries, huckleberries, and grapes of divers [sic] sorts.”

The importance of trees in the new Penn’s Woods is only elevated when you remember the names with which he christened the streets of Philadelphia’s Center City: Chestnut, Walnut, Spruce, and Pine. A street he named Sassafras was later used for horse races, so much so that its name was altered to Race.

While nature was abundant around Philadelphia, the new inhabitants impacted that nature with frightening speed. Those beavers that Thomas Yong noted? They were removed from the Philadelphia region by colonists trying to feed the frenzy for beaver-pelt top hats in Europe, disappearing from Philadelphia as early as the end of the seventeenth century—the same century that Yong noted their abundance. Otters, martens, and fishers soon followed. Deer, ubiquitous today, quickly became surprisingly scarce, as did their larger, slower cousins, the elk. All of these mammals were not only hunted by the new colonists, but by the Lenape, who of course always hunted them—sustainably. The difference now was the Lenape began trading skins and meat for European manufactured goods like pots and blankets, accelerating the loss of these mammals.

Of course, large predators are never welcome in any city, so wolves, lynx, cougars, and more were immediately pushed back, along with the innumerable trees that were felled to build and heat the growing metropolis.

“Filth of Various Kinds”

Dock Creek once flowed through the city where today’s Dock Street stands—explaining that street’s quirky diagonal slice through Penn’s tidy grid. The creek was used as an open sewer for industrial effluent from tanneries and slaughterhouses. In 1739, only 58 years into the green country town’s holy experiment, a young Ben Franklin petitioned the Pennsylvania General Assembly to remove those polluters who were harming both creek and river (and likely stinking out his Market Street print shop). He wrote in his gazette that the creek was choked with “hair, horns, guts and skins,” and that if a fish swam in the creek it would “soon float belly up.”

In another publication, residents described Dock Creek as “a Receptacle for the Carcasses of dead Dogs, and other Carrion, and Filth of various kinds, which laying exposed to the Sun and Air putrefy and become extremely offensive and injurious to the Health of the Inhabitants.” A visiting Englishman wrote a 1769 travelogue of America and dismissed the Philadelphia stretch of the Delaware as “a mess.”

Between 1762 and 1769, an older, wiser Ben Franklin led a committee to regulate water pollution in the city. Not long after the Revolution, Dock Street was covered over, a bandage over a very sore wound. Franklin died in 1790, and his will set aside funds for a pipeline to provide Philadelphians with fresh, clean water; its construction led to the creation of the Philadelphia Water Commission, the forerunner of the Philadelphia Water Department. For his public health advocacy, Franklin has been christened “America’s first environmentalist” by many, another feather in his very crowded cap.

Fairmount Water Works was built to supply clean drinking water to the city.

In less than a century, Philadelphia had strayed far from the green country town that would “always be wholesome.” Still, city government came up with a wonderful answer that likely would have been approved by Penn himself, one that added some luster to Philadelphia’s diminished image. From 1812 to 1815, the Fairmount Water Works was built on the banks of the Schuylkill to supply drinking water to the city, with river water being pumped to the top of the “Faire Mount.” Fairmount Dam was also built across the river then, to both direct water to the mill house and prevent saltwater from the tidal Schuylkill reaching the drinking water source.

When commercial development threatened the large estates just upriver from the water works, to protect its drinking water the city government smartly began purchasing these properties, including Lemon Hill in 1843 and the adjoining Sedgeley estate in 1857. Fairmount Park was thus born. Today, counting neighborhood parks, the Philadelphia park system encompasses more than 8000 acres, including what the city calls “watershed parks” along large streams—Wissahickon Valley, Cobbs Creek, and Pennypack Parks—to protect water and happily preserve habitat as well.

A City on the Fall Line

Not only was Philadelphia founded between two rivers, the city straddles two great geological provinces—which is the reason it is located here. The cities of Trenton, Baltimore, and Richmond reflect the same story: they bridge these same two geological worlds.

To get a better understanding of this, let’s go back—way back—in time, about 280 million years ago, 60 million years before the very first dinosaurs. At that time, the Earth’s ever-shifting crustal plates aligned so that all of the present continents slowly crushed into each other to form the supercontinent Pangaea, which literally means “all the land.” As today’s Europe and Africa crunched against North America, the continents buckled and folded not unlike cars in a head-on, albeit very slow motion, collision. As a result, the Appalachian Mountains were pushed up west of Philadelphia and down the whole length of North America.

Such collisions are still occurring today, notably where Italy is pushing against Europe to form the Alps and where India has been ramming Asia for millennia to build the Himalayas. But this mountain-building event took place so long ago that the Appalachians—once as tall and jagged as the Himalayas—have since become eroded and worn down, with gravity, wind, water, and weather conspiring to slowly smoothen their jagged edges. West of Philadelphia are the hard-rock remnants of the roots of these ancient mountains; east of Philadelphia, New Jersey sits atop soft sediments eroded off of those mountains. Hold those thoughts for a moment.

Consider how different the landscape is as you leave Philadelphia and drive to the Jersey shore. Southern New Jersey, in a huge change from Pennsylvania, is suddenly flat, sandy pinelands, radically different from Philly. And there are few rocks in southern New Jersey. What happened here?

As Pangaea split up, Europe and Africa moved away from North America, opening the Atlantic Ocean—which is still widening today. In fact, the Atlantic is growing at about the rate your fingernails do. And the ocean is a dynamic system that continually changes as well. Essentially, New Jersey’s sands were deposited as sediments at the bottom of the post-Pangaea ocean, as there were times when the Atlantic covered southern New Jersey, even coming very close to today’s Philadelphia, and times like the Ice Age when land extended much further east.

From Belmont Plateau, as you look down on the Philadelphia skyline, you are standing on the Piedmont and looking into the Atlantic Coastal Plain.

Welcome to the Atlantic Coastal Plain, a province that begins in Massachusetts and stretches into Florida. It includes most of southern and even central New Jersey and all of Delaware, plus the eastern portions of coastal states from Maryland southward. The land here is typically flat, the soils sandy, and the sediments derived from ocean beds. Much of Philadelphia, including Center City and the Northeast, is located in the Coastal Plain, on this province’s western fringe.

This 1870 watercolor by Augustus Kollner depicts the Roberts Mill built on Wingohocking Creek in 1683 in Germantown, the state’s first grist mill.

Perched on the Fall Line

Starting just beyond the Philadelphia Museum of Art is the Piedmont, a large and important geological province that slices through Philadelphia’s heart. Its name derived from the Italian word meaning “foothill,” the Piedmont’s rocks are remnants of older and eroded mountain chains that predated the rise of the Appalachians. The Piedmont is made up of low plateaus and hills—neither of which could ever be called mountains. This province begins in central New Jersey and extends south all the way into Alabama.

The eastern edge of the Piedmont is the Fall Line, a dramatic drop-off between the hard rocks of the Piedmont and the soft sediments of the Coastal Plain. The best place to see the Fall Line is by standing at Belmont Plateau, or “the Plat,” as high school kids in the area call it, and looking east, Center City beautifully splayed out in front of you. Or drive up Ridge Avenue west from Kelly Drive to head into the Wissahickon neighborhood of Roxborough: you are climbing the Fall Line. Likewise, a drive up Green Lane, the famed wall in Manayunk bike races, is ascending this feature.

The Delaware River seems to parallel the Fall Line for much of its run; so does the New Jersey Turnpike. In fact, have you ever noticed that the turnpike seems to magically delineate the line between snow and rain during many winter storms? Blame the Fall Line again. “While elevations along the Fall Line,” writes weather reporter Anthony R. Wood, “may be only a few hundred feet above sea level, those elevations can make dramatic differences in a storm.” The air is slightly colder atop the Piedmont than on the Coastal Plain below, and that can make a measurable difference in snowfall depths.

The Fall Line crosses the Schuylkill River from West Philadelphia into East Falls, creating the Falls of the Schuylkill, a once-famous geological formation that gave the East Falls neighborhood its name. The Lenape called this site Ganshewahanna, which translates as “noisy water.”

In 1820, a dam at the Fairmount Water Works was erected across the Schuylkill River to create a source of dependable drinking water for the city. The project raised the height of the river behind the dam, flooding the falls. Nowadays, only a few rocks poking out of the river hint at what the falls once looked like, and most Philadelphians have long forgotten how the East Falls neighborhood earned its name—or how the falls there once roared.

Geology, of course, influences so many things. Water-powered mills were among the region’s first industries after colonial settlement. As water tumbled down the Fall Line from one province to another, its velocity turned water wheels across the region, grinding flour, sawing logs, making cloth and paper, and so much more.

Remember that I asked you to hold those thoughts about the Piedmont and the Coastal Plain? Philadelphia sits on the Fall Line, a perfect location for commerce. Think back to the early colonial history of a developing America and the importance of boats in that era. Where rivers like the Schuylkill cross the Fall Line, waterfalls form. Cities develop at these locations because ships reach the inland limit of navigation—and cargo must be off-loaded for land-based transport, which back then involved horses. Philadelphia, Wilmington, Trenton, and Princeton are all sitting on the Fall Line, as are Baltimore, Richmond, Washington, D.C., Raleigh, and Tuscaloosa. While Philadelphia was planned by William Penn, most of these other cities organically evolved where the Piedmont spills into the Coastal Plain, as that was a logical place for ships to meet wagons, and each city provided the infrastructure for the two to meet.

“So Remarkable a Loveliness”

Now let’s complicate and amplify the story hidden in the rocks by visiting Philadelphia’s most dramatic rock formations in Wissahickon Valley Park, where a walk along the Forbidden Drive reveals a whole new world of steep-sided cliffs and extraordinary views. Writer Edgar Allan Poe, a one-time Philadelphian, once wrote to a friend, “now the Wissahickon is of so remarkable a loveliness that, were it flowing in England, it would be the theme of every bard.”

The city’s Grand Canyon, the Wissahickon Valley formed from the exact same forces as that western landmark: as the land around it rose from tectonic activity, the stream eroded the rock while staying in its ancient bed, just like the Colorado River scouring down deeper into the Grand Canyon. Wissahickon Creek has been flowing through this valley for about a million years, geologists think.

Sarah West, a retired science teacher who has led dozens of geology walks along Wissahickon Creek, says the valley is “a fascinating place, with some mysterious things about it. For example, it is a backwards creek. It arises in gently rolling land, and its major headwater is runoff from a parking lot at the Montgomery Mall. It ends in this little mountainous gorge. That’s exactly backwards. Most creeks start in mountainous gorges, then flow through gently rolling land, and then maybe some kind of marshy area and out into a bigger body of water. But the Wissahickon doesn’t follow that pattern.” For Sarah, this is a clear signal that something is different.

Lincoln Drive slicing through the Wissahickon Valley, Philadelphia’s Grand Canyon and the remnants of an ancient mountain system.

The Earth’s crust rests on plates that were moving long before Pangaea—and continue moving today. Wissahickon Valley’s rock outcrops are the roots of an ancient massive mountainous land more than 500 million years old, formed from rocks laid down at the bottom of an ancient ocean, the Iapetus (who in mythology is the father of Atlantis); this ocean was a precursor of the Atlantic. So Wissahickon rocks are twice as old as that Pangaea collision.

As the Iapetus Ocean closed, a chain of volcanic islands in the ocean were pushed up onto the North American continent, and then buried and folded onto.


  • "This guidebook by Mike Weilbacher includes the region's natural history, 101 species to know, and 19 field trips in the city, surrounding suburbs, and South Jersey."—Philadelphia Inquirer
  • "Wild Philly will help you to discover new things about the animal and plant life throughout the region."—Broad Street Books

On Sale
Feb 28, 2023
Page Count
368 pages
Timber Press

Mike Weilbacher

Mike Weilbacher

About the Author

Mike Weilbacher is the executive director of the Schuylkill Center for Environmental Education in Philadelphia, the region’s largest and oldest nature center. An environmental educator with 40 years of experience teaching through nature walks, lectures, newspaper essays, theatrical performances, and radio. Since 1988, he has appeared as “Mike the All-Natural Science Guy” on an award-winning live children’s radio show, talking to children about nature and the environment. Mike has been a keynote speaker at state and national education conferences, speaking before groups like the National Science Teachers Association, the Pennsylvania Association for Environmental Educators, the National Association of Interpretation, and the Association of Nature Center Administrators.

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