What happened after a Granite Falls man found ancient bison bones in his pasture?

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GRANITE FALLS, MINN. ‐ Nearly 8,000 years ago, in the wild expanse of what is now southwestern Minnesota, a primal drama of survival unfolded.

Early Plains Archaic hunters — ancestors of today’s Indigenous people — ambushed a herd of massive, now-extinct bison. The remnants of this ancient hunt, the bison bones and stone tools, lay buried for thousands of years in the Minnesota River Valley.

Then, in 1988 a Granite Falls man named LeRoy Peterson found bones through pure chance, while excavating a garbage pit in his pasture. The archaeological discovery sparked excitement throughout the state, drawing scientists, students, newspaper reporters and curious onlookers eager for a glimpse into the distant past.

Archaeologists found not just ancient bison bones, but also the spearheads used by the hunters that brought them down, alongside the knives and chopping tools used to butcher their meat and hides.

Now known as the Peterson site, it has been recognized as one of the oldest known bison kill sites in Minnesota, and one of a handful of Early Plains Archaic bison kill and processing sites in America.

Three decades after the discovery, Delores Gustafson has been wondering about what happened after the digging stopped. Gustafson wrote to Curious Minnesota, the Strib’s reader-driven reporting project, to ask: “What is the status of this site today?”

It is now a serene grass pasture with outcroppings of granite, just outside the city. The dig left parts of the site undisturbed.

Meanwhile, the unearthed bones and artifacts — owned by the Petersons but loaned to the Minnesota Historical Society — continue to fuel research.

The Peterson collection is “one of its more popular ones” for researchers, said Jennifer Rankin, the historical society’s director of archaeology. They’re examined by university students, geologists, biologists, and even paleoethnobotanists — scientists who study past human uses of plants.

The site offered up a few mysteries that are still unsolved, she said.

LeRoy and Janet Peterson, the landowners who stumbled upon a window to the ancient past, still live on the property in Granite Falls.

A sign marks the spot where LeRoy Peterson unearthed the bison bones that August.

LeRoy, now 85, and Janet Peterson, 75, keep a collection of newspaper clippings that chronicle the whirlwind years after finding the bones.

“That was exciting,” LeRoy Peterson recalled. “To find something like that.”

LeRoy, who worked in maintenance for the county, and Janet, a beautician for 50 years, saw their quiet life become the focus of scientific endeavor. For three years after his discovery, their pasture hosted a steady stream of archaeologists and students.

“They came from Minneapolis and they brought a whole crew,” Janet Peterson said. She recalled giving hot cocoa to the college students, some of whom stayed at her parents’ home during the digging.

Her beauty shop customers couldn’t help but ask about it. “While you’re busy doing the hair, you know, you got time to talk,” she said.

The final field excavation wrapped up in October 1990 as harsh weather set in, and the site was backfilled.

The question of when to stop digging is a complicated but critical one, said Rankin.

Archaeology is, by its nature, a destructive science, she said. Once an artifact is removed from the soil, its original context is gone forever. Archaeologists ask themselves if additional digging will lead to new information, or more of the same.

“Generally, for archaeologists, we really only look at a small percentage of an archaeological site,” Rankin said.

Leaving parts of a site undisturbed also allows future generations, armed with potentially better technology and new ways of thinking, a chance to take a look for themselves, Rankin said.

She added that practicalities like funding and limited archeological resources around the state also play a role in the scope of a dig.

Much of the work happens in the laboratory after the digging stops, Rankin said. The Peterson site in Granite Falls is a good example of this.

Archaeologists found nearly 4,000 pieces of bison bones, part of a minimum of 12 bison that were hunted down and butchered, Steven R. Kuehn wrote in a 2016 report published in The Minnesota Archaeologist.

The site also yielded about 1,800 stone artifacts, including the actual spear points used in the hunt, various cutting tools and choppers for dismembering the animals.

Radiocarbon dating of bone and charcoal samples places the hunt as happening in late fall around 7,700 to 8,000 years ago, according to the report.

For a time, the bison bones from the Peterson site were kept at a local museum. After it flooded in 1997, most of the boxes of bones eventually found a secure, climate-controlled home with the Minnesota Historical Society at the Minnesota History Center.

Could researchers return to the Peterson property to dig once more? Rankin at the Minnesota Historical Society believes it’s possible.

Perhaps a new generation of archeologists will find answers to some of the site’s enduring questions, Rankin said. She noted that a single canine tooth was found among the thousands of bison bones. Was it from a domesticated dog that aided the hunters, or a coyote scavenging after the fact?

Other researchers have wondered if there’s a campsite, perhaps still buried and undiscovered, near where the bison were killed.

“We’ve always been open if an archaeological group wanted to come and revisit,” Janet Peterson said.

She has become an ambassador for the site, sharing its story at museums across the state and joining her local historical society. The Petersons even welcome schoolchildren on field trips. They have not made money off the site, they said.

Whenever she mows the pasture, Janet Peterson wonders what else can still be found underneath the soil. Perhaps more bison bones — and, though they were around much earlier, maybe a woolly mammoth?

“Come on, let’s think big,” she said.

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