Ten years ago, this was just a big hole in the ground behind a Lowe’s home improvement store in southern New Jersey, an unlikely place to find what might be one of the world’s most important fossil sites.

But 66 million years ago, tantalizingly close in time to when the dinosaurs went extinct, a multitude of sea creatures died here — a “mass death assemblage” — and sank to the bottom of what was then a shallow sea.

Because of its prehistoric past as a possible mass extinction gravesite, the hole that was once a quarry has become the Edelman Fossil Park & Museum.

Built in Mantua, N.J., about 20 miles from Philadelphia, the museum welcomed its first paying customers this past weekend. For Kenneth Lacovara, a professor of paleontology and geology at nearby Rowan University and the museum’s executive director, it is the culmination of a decade of work.

“We’re doing so much here that I think has never been done in any museum,” said Dr. Lacovara, best known in paleontology for the discovery of Dreadnoughtus, one of the largest dinosaurs ever.

The fossils come with a hard-to-miss message from Dr. Lacovara, one that makes direct connections between the mass extinction 66 million years ago and today’s rapidly changing climate, which is putting many species in danger of dying out.

The museum’s motto is “Discover the past, protect the future.”

“That’s really the thrust of this place,” Dr. Lacovara said. “We need to act, and we need to act now, and every day of inaction or worse, every day that we go backwards, is a burden that we are placing on future generations.”

For decades, the Inversand Company had scooped from the quarry a dark greenish sand called marl, used for the treatment of water and soil. Tightened environmental regulations turned the site into a money loser, and Inversand looked to close it.

Mantua had hoped that a developer would turn the pit into more suburban homes and shopping. But the Great Recession stalled those plans, and the quarry remained a hole in the ground.

The mining of marl had exposed prehistoric sediments that extend throughout this part of South Jersey, but are typically inconveniently buried more than 40 feet underground.

Dr. Lacovara, then at Drexel University in Philadelphia, had started visiting the site, which included a fossil-laden layer that appeared to coincide with the mass extinction 66 million years ago. Fossils of anything that died that day are scant within the extinction layer, because the conditions needed to preserve bones are rare.

“This is something that I personally and lots of other paleontologists have been looking for all around the world,” said Dr. Lacovara, adding that he had sought such a layer in southern Patagonia, the foothills of the Himalayas and elsewhere.

“And I found it behind the Lowe’s in New Jersey,” he said.

More than 100,000 fossils representing 100 species have been carefully excavated from the quarry and cataloged.

Until the pandemic, the site opened once a year to the public for a community fossil dig, allowing people to collect fossils from sediments above the mass extinction layer.

Rowan University bought the site in 2015 for just under $2 million and lured Dr. Lacovara, who had graduated from the school when it was known as Glassboro State College, to join its faculty as the dean of the new School of Earth and Environment. Rowan also bought into Dr. Lacovara’s vision of building a museum.

“This is going to be a place to motivate young minds to become scientists,” Ali Houshmand, the president of Rowan, said in remarks at the start of the media tour.

Jean and Ric Edelman, founders of a financial advisory firm and also graduates of Glassboro State, contributed $25 million of the $75 million Rowan needed to build it.

“We immediately recognized that this had the potential to be a world-class destination,” Mr. Edelman said.

There is plenty of what one would expect to find in a dinosaur museum, which overlooks the fossil site in the former quarry. Near the ticket kiosks are skeletons of creatures that lived along the east coast of North America during the Cretaceous period. A mosasaur, a ferocious marine reptile, hangs from the ceiling, and a Dryptosaurus, a relative of T. rex, poses menacingly.

The museum highlights how some of the earliest dinosaur discoveries were made in New Jersey. The first nearly complete dinosaur skeleton — a duck-billed hadrosaur — was dug up in a quarry in Haddonfield in 1858. Dryptosaurus was the first tyrannosaur to be discovered, in 1866, just a mile from the museum.

Visitors walk a winding path through three galleries in the museum.

In the first gallery, an introductory movie provides perspective on just how mind-bogglingly old our planet is.

If the 4.5-billion-year history of Earth were a 1,000-page book, the entire 10,000 years of human civilization would be covered by just the last word on the last page. That sense of “deep time” is meant to set up visitors for an understanding of how unnaturally quickly Earth’s climate is changing now.

Life-size re-creations of dinosaurs, big and not so big, fill the gallery. In the warmth of the late Cretaceous, sea levels were much higher and North America was a series of islands. In one, a big, angry plant-eater known as Astrodon stomps a juvenile meat-eater, Acrocanthosaurus, to death.

“We want to show the gritty underbelly of the dinosaur world,” Dr. Lacovara said.

The next gallery highlights the marine creatures that lived in the seas here, including sea turtles, sharks and saber-toothed salmon. This part of New Jersey was about 70 feet underwater and 15 to 30 miles offshore. “In this gallery, everything you see here is something that was found on the property,” Dr. Lacovara said.

That includes the fearsome mosasaurs.

“I would say it’s a statistical near certainty that at some point in time, a mosasaur of this size was at that exact location,” Dr. Lacovara said, pointing to a re-creation of the creature.

Visitors then enter the Hall of Extinction and Hope. It shows the devastation that enveloped Earth after an asteroid struck the Gulf of Mexico off the Yucatán Peninsula, the fifth mass extinction in the planet’s history.

Then it turns to the present, which many other scientists describe as the sixth extinction as species struggle to adapt to the changes humans have made to the planet, including the destruction of habitats and global warming spurred by the rise in greenhouse gases released from the burning of fossil fuels.

One interactive exhibit shows the sharp rise in global temperatures over the past few centuries and allows a visitor to compare that curve with possible natural causes like sunspots, volcanic eruptions and cyclical changes in Earth’s orbit.

“None of those things explain the temperature variation,” Dr. Lacovara said.

But the simultaneous rise of temperature and greenhouse gases are “almost an exact correlation,” he said. “So at that point, you can draw your own conclusions.”

He said he wanted people to learn by examining the data themselves. “Not everybody is going to connect the dots,” Dr. Lacovara said, “but if they’re inclined to, our job is to help.”

At the last station, kiosks offer visitors information about how they can take action to offset climate change. “Because hope without action is really despair,” Dr. Lacovara said. “You’re all set up to make a positive change in the world before you walk out the doors of the museum.”

How might this message play in a time when President Trump calls climate change a hoax and his administration is dismantling projects and research aiming to move away from fossil fuels?

“I guess we’ll see when the museum opens,” said Kelly Stoetzel, the managing director who oversees the day-to-day running of the museum. It expects to draw 200,000 visitors a year.

She said she was interested in hearing the reactions of visitors who are skeptical that the planet is undergoing rapid changes.

“When they come in and they learn the science, can they be convinced to consider something different?” Ms. Stoetzel said. “Maybe.”

For Dr. Lacovara, the message is simple. “You can’t love what you don’t know,” he said. “And we’re hoping to make people fall in love with this amazing planet that we have so that they take action to protect it.”

The museum’s learn-by-doing ethos will allow visitors to become paleontologists for a day. For an extra fee, from May through October, visitors will be able to dig through the quarry sands for fossils that they can take home.

The museum also includes fun flourishes. Take the elevator between its two floors, and you’ll hear a snippet of popular singers of the 1950s and 1960s like Dean Martin, whose given name was Dino. Thus, “dino lounge” music.

At the entrance is the pronouncement, “This facility is smoke-free, weapons-free and asteroid free (for the last 66 million years).”

Dr. Lacovara is also proud of the glass used for the exterior windows, because it keeps modern-day dinosaurs — birds — from fatally flying into them.

“What I really love about it is, it relies on evolutionary principles,” Dr. Lacovara said.

The eyes of the first vertebrate animals, predating both mammals and dinosaurs, possessed four color receptors — for red, blue, green and ultraviolet light.

Birds, which are dinosaurs that survived the mass extinction, still have ultraviolet receptors in their eyes. They see images of spider webs that are imprinted on the museum’s glass, and they safely fly away.

“If you come up and you catch just the right angle, you can kind of see it,” Dr. Lacovara said.

Mammals, however, lost the ability to see ultraviolet light, because when they arose more than 200 million years ago, they were small creatures that scurried about at night — better not to be seen and eaten by the dinosaurs. There is not a lot of ultraviolet light at night, and in mammals, the gene that encodes that receptor in the eye was co-opted by the olfactory system.

As a result, mammals tend to have a good sense of taste and smell but cannot see ultraviolet light.

“To us mammals, this looks like clear glass,” Dr. Lacovara said. “And I know this because the forklift truck driver who drove through one of these panes was a mammal.”

With the museum now open, Dr. Lacovara hopes to turn his attention toward proving that the mass death assemblage in the quarry pit indeed consists of animals killed in the planet-wide cataclysm that followed the asteroid strike.

That has been hard to settle, however, because creatures burrowing in the sea bottom churned up the sediments. As a result, the marker of the extinction — a layer containing substantial amounts of iridium, an element concentrated in asteroids and comets — is fuzzy.

“It’s almost like looking through a shower door at something,” Dr. Lacovara said.

He said he had all the data he needed, but work on the museum had not left him time to finish writing the papers.

“This has been all-consuming,” Dr. Lacovara said.