I ride shotgun in a utility vehicle, holding archaeologist Jarrod Burks’ laptop as he drives across a farm in southern Ohio, over the shaved stubble of corn stalks. Back and forth we go at 18 miles per hour, each pass making a T roughly two yards wide and 100 yards long and tall. We’re pulling a trailer with five magnetometers, which measure the Earth’s magnetic field at surface level and below. Burks is using them to look for evidence of ancient Native American activity.
I wouldn’t have known that this location, known as Snake Den, was an archaeological site if Burks hadn’t invited me to meet him there. I wouldn’t have known that the mounds, not much taller than I am, among the trees are 2,000-year-old burial mounds, not natural knolls. And I wouldn’t have known about the mysteries Burks’ magnetometers have found in previous trips to this farm: ancient features called enclosures, which make me think of modern fence lines, except we have no idea what they once enclosed.
After an hour, Burks — director of archaeological geophysics at Ohio Valley Archaeology, Inc. and president of Heartland Earthworks Conservancy — climbs out of the vehicle and downloads the magnetometers’ data. On his laptop, we look at a map of the ground we drove over, with dark blotches representing differences in the magnetic field. Blotches forming an obvious shape could mean a discovery, as when Burks found an enclosure shaped like a “squircle”: a square with rounded corners.
There will be no such discovery today, which is both good news and bad. Archaeologists learn where not to dig by confirming, as we did today, that nothing is there. But they also sometimes realize that something used to be there, but modern development wiped it away.
For more than 12,000 years before Europeans arrived in North America, Native American cultures dotted what is now the American Midwest. Some subsisted by hunting and moved with the seasons. Some formed complex civilizations whose populations grew to thousands of people. They left behind countless relics, from pottery shards to arrowheads to delicately carved artwork. They left architectural remnants, too, in the form of earthworks like the ones I drove over with Burks, and also mounds shaped like animals, conical mounds and burial mounds.
When we think of archaeological sites, we often imagine vast areas cordoned off, like the massive excavations in Rome, or hidden entirely from view, like the Mayan ruins beneath dense forests in Guatemala.
But at Snake Den and other places around the world, the evidence of native cultures is sitting in plain sight, in land that has been used and reused so many times that it’s sometimes easier to find evidence of the distant past than the recent one. Finding those sites has become the passionate work of both professional and amateur archaeologists, using technology that has become increasingly accessible.
For an archaeologist like Burks, there is always more to discover. “When he stops and yells holy sh—,” says Al Tonetti, a fellow archaeologist who really stopped at the sh sound, “that’s when I know.”
But how much access Burks and others will have to those holy sh moments is an open question. Many property owners, wary of the consequences if something is found on their property, are reluctant to let archaeologists on site to look. And so archaeologists face a baffling conundrum: They are more equipped than ever to uncover lost mysteries and frustratingly unable to do so. As we find more archaeological treasures from the past world, we’re more likely to find them bumping into the present.
This issue is becoming more pressing, in part because of advances in technology over the past 20 years. Instead of sifting through mounds of dirt, archaeologists now do the same with data, which is collected via ground-penetrating radar, photogrammetry, magnetometry, and a laser technology called lidar.
Matt Woodlief, a lecturer at Northeastern University who teaches a course on radar and lidar remote sensing, describes using lidar as sweeping the ground, only with lasers instead of broom bristles that collect data instead of dirt. The millions of data points that come back, each showing the velocity and angle of the laser’s return, can be translated into a 3D map of whatever was swept. That means more potential discovery, with far less effort.
It also means more opportunities for what Burks calls “earthwork fever” — an obsession that non-archaeologists get after they visit earthwork sites. A friend of his spends many lunch hours poring over Google Earth photos, looking for unmapped sites. I don’t have it quite that bad (yet), but I came down with mild symptoms after taking my wife and kids to Cahokia Mounds State Historic Site, probably the most important mound site in the United States. Covering 3.5 square miles, Cahokia sits across the Mississippi River from St. Louis in southwestern Illinois. It comprises 72 platform, ridgetop and conical mounds, including Monks Mound, a four-tiered structure, 98 feet tall — the largest earthen structure in the country.
The Grand Plaza, a 40-acre square plot, sits just south of Monks Mound. It was used, in part, as a sports field. The people who lived there played a game called chunkey, which was something like skeet shooting, except not in the air: someone rolled a stone on the ground, and competitors threw their spears at it.
At its peak, from A.D. 1050 to 1200, Cahokia was the biggest city north of Mexico. Estimates put the population as high as 20,000 — more than London at the time. Counting the surrounding area, it might have been more than double that. I live in the St. Louis suburbs; there were suburban dads here more than 1,000 years before me.
“Festivals at Cahokia were mostly centered around group meals where people feasted on barbecues of deer, bison, squirrels, and even swans. Centuries later, archaeologists found huge party trash pits full of fire-cracked bones and broken dishes.”Annalee Newitz, in the 2021 book Four Lost Cities: A Secret History of the Urban Age
Farms separated neighborhoods (which is true today, too, at the outer reaches of the suburbs), and mounds became gathering places. Tim Pauketat, an archaeologist at the University of Illinois at Urbana-Champaign, believes Cahokia was a spiritual center.
Cahokians loved a party, according to the 2021 book, Four Lost Cities: A Secret History of the Urban Age, by Annalee Newitz. “Festivals at Cahokia were mostly centered around group meals where people feasted on barbecues of deer, bison, squirrels, and even swans,” Newitz writes. “Centuries later, archaeologists found huge party trash pits full of fire-cracked bones and broken dishes.”
In archaeological searches, relics of modern life often mix with artifacts from the ancient. In 2020, a team of researchers from St. Louis University compared the results of lidar and photogrammetry created by drone images at Cahokia. The remote sensing revealed the razed foundations of houses from a 1940s-era subdivision, a centimeter or two tall, hidden by the grass. The team had walked right over that exact spot and seen nothing.
Yes, a subdivision was once built on arguably the pre-eminent archaeological site in the country. So was a drive-in movie theater; it was called Mounds Drive-in and showed X-rated movies in the 1970s. Both were bulldozed in the 1980s. There’s now an effort in Congress to make Cahokia a national park.
But while sites like Cahokia are protected, there are many other places where ancient mounds are simply part of the landscape on private land. And as technology has matured, so has our knowledge of where these features exist. In 1914, an atlas cataloged 587 enclosure sites in Ohio, Burks tells me. Now, archaeologists know there are dozens more enclosures in the state, and many more features at other known locations.
In 2021, Portland State University researchers Tia Cody and Shelby Anderson created a mound detection predictive model using lidar and aerial imagery and deployed it in Oregon’s forested Willamette Valley. The model successfully identified every previously known mound in the surveyed area, and 44% of the features it tagged as potential mounds were verified as mounds via fieldwork. (Among the unverified mounds were a few pitching mounds on baseball fields.)
Many of these discoveries amplify what archaeologists already know, as if a baseball archivist found lost video of Babe Ruth hitting home runs. But some discoveries have been more powerful than that.
Consider Burks’ discovery at Fort Ancient, a 3.5-mile-long enclosure on a hilltop in Warren County, Ohio, built by the Hopewell culture around 2,000 years ago. The site has been studied for 150 years. But in 2005, Burks discovered a feature, dubbed Moorehead Circle, where ritual ceremonies had been held. It included three circles of posts, trenches and many burned layers — all of which combined for an enormous holy sh moment.
Indeed, the more Burks finds, the more he wonders what he’s missing. He points out a spot in the cornfield at Snake Den where the magnetometer found a long-buried rectangle-shaped enclosure. “You can’t see that rectangle. If there’s that kind of invisible thing at a known site …” his voice trails as he ponders the possibilities. “Ohio’s a big place. How many totally unknown earthworks sites are there in this region? We’ve already shown that there are a lot.”
I travel to expose my ignorance to light, and my visits to earthwork sites in Ohio, Missouri, Illinois, and Wisconsin have been blinding. I love to hike deep in the woods, far from everywhere, and imagine nobody has ever stood there. PFFT! I canoed a 50-mile stretch of the Wisconsin River last summer near several mound locations. An archaeologist told me that no matter where I camped on the banks, Native Americans had camped there thousands of years ago, because the Wisconsin River acted as one leg of a watery interstate highway system connecting the Gulf of Mexico with the Atlantic Ocean via the Mississippi River basin and the Great Lakes.
At Snake Den — so named because researchers found evidence snakes had made their home in its mounds long after humans abandoned them — the layers of civilization surrounded me. In the distance, 30 miles away, rose the skyline of the city of Columbus. (The irony of encountering that name as I reported on land use in America before European contact didn’t occur to me until later.)
Behind me, underground, a line of pits dated to 900 B.C. (according to carbon dating, at least, though Burks wonders if that measurement is accurate). The burial mounds to my left — in which eight bodies and one set of cremated remains were found — were built between 100 B.C. and A.D. 250. The farm under which this all rests originated in about 1820. A gas line from 1930 runs under the property. This little farm in the-middle-of-nowhere Ohio has been used and abandoned who knows how many times, by who knows how many groups, over nearly 3,000 years.
John Low, a citizen of the Pokagon Band of Potawatomi, a professor at the Ohio State University and the director of the Newark Earthworks Center in Newark, Ohio, isn’t surprised at that level of turnover. “That’s how history works,” he says. “There’s important stuff built on top of other important stuff.”
Newark Earthworks Complex, built by the Hopewell in the first four centuries A.D., once took up four square miles; development has erased much of it. It shares ground today with a golf course. So apparently, we have built less-than-important stuff on top of important stuff. But even that, Low says, is looking at it with a Western point of view. To the people who built these mounds, it’s not the “stuff” that makes a site important, Low says.
“Before the mounds and the earthworks were built, the sites were already sacred. They’re not sacred by human intervention, not sacred by human designation,” Low says. “In the Western world, we build a church, or a mosque, or a temple, and we call that sacred until we’re done using it, and then we move on. These earthworks and mounds are built to celebrate the pre-existing sacredness of the site.”
The structures that marked those sacred sites are disappearing, destroyed by modern development or plowed under by farmers. Wisconsin once was home to tens of thousands of mounds, an estimated 80% of which have been destroyed. Cartographers have mapped earthworks’ locations for more than 100 years, and even locations on those maps are disappearing.
“This has occurred too many times across the state. I’ll pull up a surface model from the lidar data and I see nothing,” says Mike Farkas, a research scientist for archaeological data at the Illinois State Archaeological Survey. “The site and mounds are gone. I mean entirely gone, erased from the landscape. Archaeological sites are being destroyed, and it is just so difficult to get most people to notice or even care. I see it like a page being lost from the book of our history.”
Woodlief says lidar and other remote sensing technologies will continue to become cheaper and easier to use, making it easier for professionals and amateurs drawn to these sites to discover what’s there before it gets destroyed. But for private landowners, there are disincentives to investigating their property further. Yet ignoring remote sensing has consequences, too, if you later have to dig on your property and come across an unexpected artifact. “Once you start digging and you hit something, then the whole project stops; it becomes a whole investigation,” says Woodlief, who extracts data from remote sensing technology as an engineer for Esri, a geographic information systems company.
And getting access to private sites is already a challenge, even for university researchers. The Portland State study involved the property of 17 owners. Only three granted the researchers permission to be on site.
Burks, too, often encounters problems gaining access to private property. That’s one reason he studies Snake Den. Not only do owners Pat and Dean Barr cooperate, they participate. They were there the day I visited and eager to describe their passion for the site. Dean shaved the corn stalks to make driving the utility vehicle easier. Dean, a retired teacher, and Pat, a former elementary school librarian, care deeply about education. They want to turn Snake Den into an educational site students can visit on field trips.
Determining who decides which sites get preserved, which are worth preserving, and how to preserve them is an ongoing challenge. We are finding ancient sites all the time, changing old ones, and even creating new ones that will be studied centuries from now.
I imagine archaeologists 2,000 years from now unearthing all the places where I’ve lived: the house I lived in after college that was torn down and replaced by another one; the dingy apartment that was converted to a hair salon, and later a pastry shop. I recently moved out of a subdivision called Schrader Farms — the name itself speaks to building important stuff on top of other important stuff. I wonder if my basement will still leak in the 41st century.