The biggest, most revolutionary, and strangest dinosaur of them all was found in New Jersey

The creature slumbered in the muck for 80 million years, a giant of the Cretaceous lying beneath the feet of Garden State farmers who thought the gray slime in their pits was only good for turnips. But in the summer of 1858, a Victorian gentleman with a shovel and a grudge against ignorance dragged New Jersey—kicking and screaming—into the age of dinosaurs.

Let it be known that while California preens about its palm trees and its movie stars, it took the swamps of South Jersey to give America its first nearly complete dinosaur.

New Jersey dares to call itself the Garden State when it’s sitting on a graveyard of leviathans.

The official story, as scrubbed and polite as a tourism brochure, is this: In 1991, New Jersey officially designated Hadrosaurus foulkii as its state dinosaur. But the truth is dirtier and far more magnificent. This was no polished museum piece found in a desert. It was yanked from a marl pit—a reeking, waterlogged excavation of ancient sea floor—in Haddonfield. The man responsible, one William Parker Foulke, was a lawyer and amateur fossil hunter on vacation, which is the 19th-century equivalent of a guy fixing a carburetor for fun.

According to the state’s own account—buried on a website between recipes for tomatoes and facts about the state bird—Foulke heard a rumor that 20 years earlier, workers had hit “gigantic bones.” He spent the late summer and fall “shin-deep in gray slime,” directing a crew to dig up an animal “larger than an elephant with structural features of both a lizard and a bird.”

Let that image sink in. A proper Philly lawyer, waist-deep in primordial ooze, hauling out the leg bone of a 25-foot-long duck-billed monster. That is not a postcard from Cape May. That is the raw, unvarnished truth of New Jersey’s greatest scientific heist.

The beast was named Hadrosaurus foulkii. And it was a revelation. When the skeleton was mounted at the Academy of Natural Sciences in Philadelphia in 1868, it shattered the prevailing image of dinosaurs as sluggish, four-legged lizards. Its anatomy—the powerful pelvis, the upright stance—proved these animals walked on two legs, holding their heads high.

It was the first time the public saw a dinosaur as a dynamic, standing creature. The world of paleontology changed course right there, in a display case, because of a hunk of rock dug up from behind a farmer’s barn.

But here is where the truth gets sharp. The official story, the one polished for schoolchildren, leaves out the brutal specificity of the place. The marl pits weren’t just holes. They were the industrial scars of a state that has always been about getting its hands dirty. Marl—greensand, rich in calcium carbonate—was the 19th-century version of fracking fluid, a chemical slurry spread on fields to wring more corn out of exhausted soil. New Jersey’s towns (Marlton, Marlboro) are literal monuments to agricultural avarice.

It was this greed for fertilizer that cracked open the window to the past. And what a past it was. The fossils came from the Inner Coastal Plain, a narrow band of sediment running from Raritan Bay to the Delaware Bay. Back when Hadrosaurus lived, New Jersey was closer to the equator, a warm, shallow sea lapping at swampy lowlands.

The dinosaur died along that shoreline, sank into the greensand, and turned to stone. It wasn’t discovered by a scientist in a crisp lab coat. It was found by a farmer named John Estaugh Hopkins in 1838, who gave the strange bones away to curious visitors. For 20 years, the most important dinosaur in North America served as a conversation piece.

The lack of precision in the popular account is an insult to the men who did the actual work. It wasn’t just Foulke. He had the sense to call in a real scientist: Joseph Leidy, the Philadelphia anatomist who is the true father of American vertebrate paleontology. Leidy measured a femur four feet long.

He looked at the pelvis—the orientation of the ilium and pubis—and declared this creature walked upright. For more than a century, scientists argued about whether hadrosaurs were aquatic, using their duck-bills to filter water plants.

We now know Leidy was right about the posture, but wrong about the swimming. Hadrosaurus was a facultative biped. It walked on four legs most of the time, like a cow, but could rear up on its hind legs when it needed to run or reach high branches.

And don’t let the polite term “duck-billed” fool you. This was a weapon. Behind that toothless beak were “dental batteries”—hundreds of self-sharpening teeth packed into a crushing mill designed to grind cycads and conifers into pulp. This was a herbivore with the jaw strength of a backhoe. The only thing more terrifying than a meat-eater is a plant-eater that can digest a tree.

The Hadrosaurus is a genus of the Hadrosaurid dinosaurs, which are known as duck-billed dinosaurs for their mouths that resemble toothless beaks. They had incredibly strong jaws in addition to hundreds of teeth arranged in intricate “dental batteries” adapted to grind fibrous plants. Since the skeletons of most hadrosaurid species lack variation, their skulls are primarily used to distinguish between them.

For example, some hadrosaurids had large bony crests on the top of their heads. An early suggestion for the function of these head crests was an air reserve to allow the dinosaur to stay underwater. In addition to the duck-like beak and possible webbed feet (which later turned out to be impressions left by soft tissue), this idea of an air reserve led to the belief that Hadrosaurus was a marine animal.

However, scientists now agree that Hadrosaurus was a terrestrial animal and that the head crest was primarily used to make low-frequency calls for long-distance communication.

California, with its usual late-to-the-party smugness, named its own hadrosaur, Augustynolophus morrisi, in 2017. Good for them. But California’s dinosaur was a child of the West, found in the 1940s.

New Jersey’s dinosaur came first. It changed everything. And the site of its discovery—the exact marl pit—was lost to suburban sprawl. Subdivision by subdivision, the birthplace of American paleontology was paved over for strip malls and cul-de-sacs.

A Boy Scout named Chris Brees had to use old maps and Leidy’s 19th-century descriptions to find it again in 1984. That’s your Eagle Scout project: rescuing the most important fossil site in North America from a Wawa parking lot.

Today, you can visit the Jean & Ric Edelman Fossil Park in Mantua Township, where you can dig with a garden trowel in the soft marl. You can see a full cast of Hadrosaurus at the New Jersey State Museum in Trenton. But the original bones are too fragile to display. They rest in the collections of the Academy of Natural Sciences, a quiet reminder that the truth of this state is not in its beaches or its boardwalks, but in the gray, stinking mud that once held the bones of a creature that refused to stay buried.

New Jersey designated this dinosaur as its official symbol in 1991. It took them 133 years to admit what the farmers always knew: This state is built on bones. And the biggest, strangest, most revolutionary one of them all was found by a lawyer up to his knees in slime. That is the precise, unvarnished, inflammatory truth. No flourish required.