Archaeologists studying a prehistoric site in Golden, Colorado, have found that people lived there thousands of years earlier than previously thought.

The site is called “Magic Mountain” after an amusement park that used to own the land back when excavations started in the 1950s.

Archaeologists like Mark Mitchell knew that people, likely nomadic hunter-gatherers, had lived and camped at the site for much of the last 5,000 years.

“It's a great place to be in the winter. You have water. Their animals congregated there. It's not too high and it's not too low. It's kind of the Goldilocks spot of the Front Range,” says Mitchell, who is research director at a non-profit, the Paleocultural Research Group, that is collaborating with the Denver Museum of Nature and Science and the University of Kansas.

Then, this past summer they went deeper than they had before, digging more than 7 feet underground.

“We dug really deep to try and see if we could get back to some of the earlier remains in the site,” says Michele Koons, curator of archaeology with the Denver Museum of Nature and Science.

They opened up a section of soil about the size of a windshield.

“And in there we found some animal bones and some chipped stone from making stone tools,” says Koons.

Preliminary results from radiocarbon dating show the soil layer containing those artifacts is 9,000 years old.

“So we know that people were there during that particular time period and they were probably eating, butchering and cooking those animals and making the stone tools in that particular location,” says Koons. She and her colleagues plan to submit their results to a scientific journal in coming months.

Mark Mitchell says sites with evidence of human habitation this old are rare.

“We have very few opportunities to see dirt that's that old and that's sort of the mantra among archaeologists who are interested in early occupation in North America," he says. "You've got to find the old dirt, and it's hard to find because it's either been eroded away or it's buried.”

Imagine thousands of years of erosion and earth-moving floods like the ones the area experienced in 2013, he says, and it's no wonder evidence can get easily displaced.

“What evidence we have of that time period is pretty sparse. It's a jigsaw puzzle with 80 percent of the pieces missing and no picture on the box,” says Mitchell.

Back then, the Ice Age had long since receded and people likely hunted an extinct species of bison that were about 30 percent bigger than the ones living today. Other than that, says Mitchell, the landscape probably looked a lot like it does today.

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City and KRCC and KUNC in Colorado.