Prehistoric Pottery Links St. Croix’s Past and Present

At an approximately 700-year-old village, the river’s bounty made for stronger ceramics.




6 minute read

“They were wonderful potters. The few complete pots that archaeologists have found are satisfyingly round or oval jars and bowls, with pale glints of crushed clam shell in their thin walls. The surface designs are geometric and often include stylized representations of hawk’s wings and serpents, combining elements of supernatural, water, earth, underworld, and sky concepts.”
– K. Kris Hirst, The Oneota Culture: Prehistoric Farmers of the American Midwest

Oneota pottery from the Sheffield Site (Photo courtesy Science Museum of Minnesota)
Oneota pottery from the Sheffield Site (Photo courtesy Science Museum of Minnesota)

About 700 years ago, someone from a village of Native American people we call the Oneota went down to the St. Croix River near present-day Marine on St. Croix and gathered mussel shells. They ground the shells into a powder, mixed it with clay, and created pottery which was used for storing food or cooking.

The mussel shells were a key innovation of Oneota potters. For a long time, they added crushed rock to their clay to prevent cracking as it dries. Around the year 1100 A.D., they switched to mussels, allowing them to make bigger, lighter pots with thinner walls. Archaeologists estimate that an Oneota pot found near La Crosse, Wisconsin could hold 15 to 20 gallons, with walls that were one-third of an inch thick.

All thanks to clam shells.

The St. Croix’s mussels are one of the river’s fascinating but under-appreciated elements. Very few places in the world have so many different kinds of mussels. There are 41 species found in the river and its tributaries – believed to be all the species that lived there before European contact. This diverse population puts the region “among the world’s greatest mussel watersheds,” according to the U.S. Fish and Wildlife Service.

To preserve mussels (or clams) today, they are strictly protected by the National Park Service. Visitors are not allowed to move mussels, alive or dead. Just picking one up and putting it back can cause it to suffocate in the sand.

For the Oneota people, mussels were simply an abundant material to use in their pots.

An Oneota outpost

Oneota arrow points from the Sheffield Site
Oneota arrow points from the Sheffield Site (Greg Seitz, St. Croix 360)

“Oneota” is a name modern archaeologists have given the group; we don’t know what they called themselves. They  lived across a territory centered on what’s now Iowa, and stretching into Illinois, Wisconsin, and Minnesota. The village near Marine on St. Croix, known as the Sheffield Site, is unique because it’s at the northern fringe of Oneota territory.

“The site is an anomaly. It’s fairly small and farther north than other settlements, but it was intensively occupied,” says Dr. Ed Fleming, the Science Museum of Minnesota’s Curator of Archaeology, who led new excavations at the site in 2013. (Fleming will present about the recent work on Saturday, Feb. 8 in St. Croix Falls; details are at the bottom of this article.)

Most Oneota villages were on rivers, and they would have traveled among the the braided channels and islands of that part of the St. Croix the same way many people do today: by canoe. Theirs were dugouts.

The Science Museum spent last summer studying and excavating part of the site. It was first explored in the 1950s by archaeologists from the University of Minnesota and Science Museum. A roving archaeologist named Theodore H. Lewis recorded 26 mounds at the location in 1885.

A new tradition today

Mary McLaughlin, Archaeology Research Assistant at the Science Museum of Minnesota, excavates a cluster of shells at the Sheffield Site.
Mary McLaughlin, Archaeology Research Assistant at the Science Museum of Minnesota, excavates a cluster of shells at the Sheffield Site. (Photo courtesy Science Museum of Minnesota)

The area where the Oneota once lived has become a hotbed of pottery once again in modern times. The St. Croix Valley is nationally-recognized for the talents of many potters who call it home.

Thousands of people have come to the valley during Mother’s Day weekend each of the past 21 years to visit pottery studios on the Minnesota Potters of the Upper St. Croix River’s annual tour, which the St. Paul Pioneer Press called “one of the country’s top ceramics events.” Quoted in that article, potter Guillermo Cuellar described its prominence, “This area is known internationally for pottery. There’s such a richness and diversity of work that’s being made here, it’s like a Mecca. I had people from 24 different states come to my studio on the last tour.”

Many potters live and work here in part because of Warren Mackenzie, an internationally-renowned potter. He has been making pots since the late 1940s and is considered the father of the “Mingei-sota” style, which was inspired by Japanese utilitarian folk pots called mingei.

Mackenzie is still working as he approaches his 90th birthday, making about 5,000 pots a year.

Hints of history

Oneota pottery fragment from the Sheffield Site.
Oneota pottery fragment from the Sheffield Site. (Greg Seitz, St. Croix 360)

Pottery is the easiest way to identify the Oneota today. “The most diagnostic trait of an Oneota population is probably the shell-tempered globular jar with a constricted orifice and a rounded bottom,” according to an article published by the University of Iowa.

The pots found at the Sheffield Site have other Oneota trademarks.

“Almost all pots at the site have interior lip notching,” Fleming says. They also have handles near the mouth, and many are decorated with lines and patterns of dots.

The Oneota were farmers and hunter-gatherers. They grew maize (corn), squash, beans, and plants with seeds that could be ground into flour. Excavations at the Sheffield Site have turned up grinding stones, ornamental copper beads, many projectile points, and hide scrapers.

The village may have been a summer settlement where they tended their crops, or a sheltered winter retreat. It isn’t known for certain. A favorite tool made from animal shoulder blades (called scapula) hints at an answer.

“They could have been farming at this site. One of their common tools for farming was a bison scapula hoe. One of those has not been found here, but there are many deer scapulas,” says Fleming.

Some things never change

Oneota mussel shell fishing lure from the Sheffield Site.
Oneota mussel shell fishing lure from the Sheffield Site. (Greg Seitz, St. Croix 360)

Pottery wasn’t the only way the Oneota used the river’s mussels. In the Science Museum’s collection from the site is a fishing lure made from a  shell, complete with an eye. It bears a resemblance to a modern-day Dardevle spoon, which remains a popular and effective lure more than 100 years after it was invented.

The Oneota would have used the lure to attract fish they could spear, perhaps northern pike, redhorse suckers, catfish, sturgeon, or musky. The same quarry many anglers pursue today, with a lure not that much different.

Whether beautiful, functional pottery, a diverse mussel population, or fishing tackle, a few things haven’t changed much along the St. Croix over the past several centuries.

Learn more

Many thanks to Dr. Ed Fleming for his research and generous sharing of information. There is of course much more to the story. Go to his presentation next weekend, sponsored by the Saint Croix National Scenic Riverway:

Saturday, February 8, 10:00 a.m.
The Sheffield site and Oneota archaeology in the St. Croix Valley
Presented by Dr. Ed Fleming, Science Museum of Minnesota

The presentation is free and open to the public. It will take place at the St. Croix River Association office, 230 South Washington Street, Unit 1, in St. Croix Falls, Wisconsin (next to the St. Croix Falls Public Library).

Reservations are encouraged but not required.  To reserve a space, call (715) 483-3300 or email


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Prehistoric Pottery Links St. Croix’s Past and Present