Chert Quarry Near Grand Meadow is Rare, Lucky Find for Archaeologists

GRAND MEADOW – Northwest of Grand Meadow near the south fork of Bear Creek, a rare archaeological site is coming to life and will soon be open for the public to explore. 

This site includes nearly 2000 pits on 200 acres of land which area residents had long speculated were created as part of a World War I test bombing range. In reality, these pits, up to 15-feet deep and some wider than 20 feet, were created much further back in time — approximately from the years 1000 to 1400 — when Native Americans dug up chert to use for tools essential to their daily lives.

An eight-acre remnant of the land will open to the public in July 2025 as the Grand Meadow Chert Quarry/Wanhi Yukan Archaeological and Cultural Preserve. The site includes a self-guided walking tour with signage in both Dakota and English made possible through a partnership between the national nonprofit Archaeological Conservancy, the Mower County Historical Society and the Dakota community at Prairie Island.

Chert was essential to Indigenous people

Chert, another word for flint, is a flaked stone that was used to make tools for daily life or weapons for hunting by chipping away at a nodule of chert until it has a serrated edge, according to Consulting Archaeologist Tom Trow, the project director and lead archaeologist for the site. (Trow is also part of a team researching Indigenous Crossroads, specifically the nearby Shooting Star Trail, in Mower County.)

“Chert is a kind of stone that lends itself to being transformed from a rock into a tool, and it’s done by hitting it with another stone,” Trow said. “It’s amazingly quick to make a stone tool when you’ve got someone who understands much about it.”

Chert was attached to a handle (called hafting) so it could be used to scrape bison hides. (Illustration by Jacquelyn Jones)

There have been at least 35 different types of chert found in Minnesota. Although chert may be many colors, Grand Meadow chert is a distinctive gray. The oldest piece of a Grand Meadow chert tool found in an archaeological context that has been verified by carbon-14 dating is 8,000 old.

Chert was an integral part of the lives of people in past times. Most had a piece of chert in their hand every single day, noted Trow, as it was key to survival for those living off the land without the iron and steel tools people use today. 

“Grand Meadow chert was the most important product to come out of southeastern Minnesota for the 400 years the quarry was active. In fact, it was the most important product ever to come out of southeastern Minnesota until Spam,” joked Trow.

Native Americans used chert for weapons to kill bison, knives to get meat off the bone and scrapers to use on the hide.

“The scraper was the most important tool in this whole process,” Trow said, “and it turns out that the way Grand Meadow chert stands out is that it is the best chert found in Minnesota for making scrapers.” 

“Hide scrapers are used for clearing the goo off the inside of skin of a dead animal, often bison,” Trow explained, as indigenous people would scrape one side and leave fur on the other for items such as a carpet or rug in the teepee, or scrape both sides for use as drum tops, shields, clothing or teepees. 

“About the bison, they used every single part,” said Trow. “This is a walking Target store. I mean it’s got absolutely everything you would need. One-stop shopping, right? They didn’t waste much of this at all.”

Oceans covered land millions of years ago

The landscape looked much different millions of years ago when the bedrock of southeastern Minnesota was formed. Oceans covered the land off and on over a massive amount of time. 

“When the ocean would come up and sit there for a few million years, billions and billions and billions of shellfish would be living and dying and dropping to the bottom and forming the sediment, and that sediment over millions of years would compress and become limestone,” Trow explained.

The signs along the Wanhi Yukan Trail are in English and Dakota. (Photo by Tom Trow)

About 385 million years ago when an ocean covering southeastern Minnesota receded, it left tidal pools, which became isolated from the oceans and slowly changed in chemistry over time. The critters that lived in them also changed, noted Trow, as their skeletal framework was made out of silica, which is what glass is made of. Over thousands of years, the remains of those critters in the pools crystalized into chert.

Then, waves of oceans came in and buried the chert layer over and over. However, the chert became readily available in river valleys with exposed bedrock walls in southeastern Minnesota and on the ground near Grand Meadow where the covering glacial till is thinner since it is on the western edge of the Driftless Area that the last glacier missed.

“It turns out that the Grand Meadow Chert Quarry is at this wonderfully coincidental spot with the lowest amount of glacial till and the highest expression of chert bed to be exposed,” said Trow. “It’s unique in this way. It’s one of the reasons that this place happened.”

How they dug the holes

Although chert from Grand Meadow was likely first used 8,000 to 10,000 years ago, Trow said that until about 1,000 years ago, there was plenty of chert available without digging. Trow speculated that people started digging holes to get chert once that supply became exhausted.

A parallel site in North Dakota called the Knife River Flint Quarries, which was also a prairie site where people dug holes to get chert, gives clues to what happened near Grand Meadow. 

Archaeologists think that people used a knife, likely made of chert, to cut the soil and take the sod off. Next, a digging stick, similar to what people used for farming along the river, was used to chop the dirt to make it loose. Then, they used a hoe made out of a bison scapula, or shoulder blade, to scrape the dirt into a basket. 

The baskets of dirt were emptied at the rim or in some cases hauled to fill a hole no longer used. Likely a team, or several families, formed a line to move the baskets along.

“Digging for Chert” painting by Red Wing Dakota artist, Cole Redhorse Taylor, depicts how Indigenous peoples dug for chert to use in their tools.

Once nodules of chert were taken out of the ground, they were probably handed up to a flint knapper, who used a hammer stone to shape the chert at a station between four to six pits. 

Archaeologists have seen evidence of hammering on rocks that were used as anvils at the Grand Meadow site. They don’t think they made the whole tools at the site, although they are still exploring that possibility, but the knappers did shape the pieces because they wanted to make sure the stone they walk away with was as light as possible, noted Trow.

Local resident first to solve mystery 

While the quarry was the largest procurement site for chert in Minnesota, “it’s been a well-kept secret,” Trow said. It was probably abandoned about 600 years ago and by the 20th century, Native American communities didn’t know about the history of the area and local farmers had no idea why all the pits were on their land.

Because the abandoned quarry was so uneven, landowners left the area covered with woods because they didn’t have the means to work the land. However, as equipment modernized in the 20th century, farmers cut the trees down and plowed the land to convert to crops. That is, except for one — the Maurice and Bernice Thorsen family, which purchased a farm in 1921 that included a portion of the pitted land still covered with trees.

“They liked having a little place to hunt turkey and deer, and they liked to have a place for the kids to play, and so the Thorsen family, bless their hearts, just left it sitting there,” said Trow.

Meanwhile, Maynard Green, a collector and amateur archaeologist who grew up just a few miles to the north and then moved to Grand Meadow, discovered many artifacts in that area, while also noticing the unusual topography.

“He knew that those woods were weird . . . everything is either a hole or a backfill pile. So, you can tell something was going on,” Trow said.

A knife made of Grand Meadow chert. (Photo by Tom Trow)

In 1952, Green wrote a letter to Lloyd Wilford, the state archaeologist, who he figured might be interested in what he thought was an ancient Native American quarry. When Wilford showed up, Green was so proud of his collection that he spent the morning showing him his favorite sites. 

They had lunch at the local cafe and at the end of lunch, Green was going to take him out to see the quarry, but when they stepped out of the cafe, Wilford saw an approaching storm and decided he better get home to the Twin Cities, never to return. 

In 1980, when Trow was the field director for the statewide archaeological survey working in southeastern Minnesota, the state archaeologist at the time handed him the letter from 1952 and said “would you go talk to this guy? He’s been waiting a long time.” 

When Trow and an associate, Lee Radzak, went to check it out, they first noticed something unusual in the plowed fields on the way to the site.

“There was a carpet of broken chert. You could see thousands of pieces scattered out there of broken chert left over from making tools, so we knew right away there had been something going on here,” said Trow. 

Some years later, Trow literally ‘dug in’ uncovering layers of chert – and history – that help us today better understand the site’s geology and its historical significance.  

In part two of this story (published June 3), we learn that more than a quarry, the Grand Meadow site was a seasonal crossroads for neighboring Indigenous people – and is shaping up to be a similarly meaningful crossroads for today’s historians, archaeologists and visitors.