On a drenching afternoon in 1969, John Olsen and his dad were driving out of the Pine Valley mountains in southern Utah’s Dixie National Forest. While pulling a horse trailer down a narrow dirt road, they hit a slick patch. The trailer slid off the road’s edge, and the two panicked horses inside the trailer nearly pulled the truck and trailer over the slope.

Very carefully, 17-year-old Olsen got out of the truck and chocked the wheels with rocks. He led the horses out of the trailer, attached leads to their bridles and guided them up and over the edge. His father pulled the outfit forward to safety, while Olsen guided the horses off the mountain.

Young Olsen later returned to the site of that slide, but not to face his fears or analyze why the trailer slid. He knew why: The truck hit a patch of wet clay.

And it was that clay specifically that brought Olsen back to the slick road.

As a boy, Olsen had been making pottery. Like most people, he used store-bought clay, but a teacher had encouraged him to try digging clay himself, like ancient cultures who came before.

He took some of that mountainside clay home and made his first pots from “native, wild” clay. Fifty-five years later, his parents still have those pots, and Olsen, who now lives in Boulder, is considered one of the world’s premier potters in the Ancestral Puebloan style.

Ancestral Puebloan pottery was made by the Anasazi and Fremont peoples in the desert Southwest from about A.D. 900 to 1300. It is hand-made from clay and other material gathered from the land. The pots are formed by one of two methods, both of which Olsen has mastered: coil-and-scrape, which comes out with a smooth surface and is painted; and corrugated, which has ridges and is not painted.

Paints are made by cooking down plant materials or crushing minerals, then applying it with a brush formed from the leaves of a yucca plant. The pots are then wood fired in a trench kiln or surface fire.

The original technique for making corrugated pots had been lost since the 1300s, even to the Native American descendants of the ancient Puebloans. Olsen is credited with rediscovering it.

Other people were making corrugated pottery before John, but it wasn’t exactly as the ancients had done it, said pottery expert Andy Ward, who is an author and host of “Andy Ward’s Ancient Pottery” website and YouTube channel. “So, John didn’t just make corrugated pots, he figured out how prehistoric people were making them,” Ward said.

While working as a heavy equipment operator, Olsen spent his free time obsessively examining the pots and potsherds in the storage room of Edge of the Cedars State Park Museum in Blanding, then replicating what he’d seen. In doing so, he rediscovered the way the Puebloans had made corrugated clay pots. His method was later vindicated by an archaeologist and an FBI fingerprint analysis expert who compared the finger and thumb prints on Olsen’s work with the pressure and direction of the prints on the ancient pieces. They were a perfect match.

“He is considered a legend among others who have interest in this field,” said Jonathan Till, curator and archaeologist at the museum. Till admires Olsen for being “both a craftsman and a researcher.”

Olsen made a living selling his replica pottery at museum gift shops across the Southwest before construction work brought him to Boulder, where he got into other primitive technologies.

One of the large, corrugated pots he sold through Anasazi State Park Museum was purchased by Boulder Outdoor Survival School (BOSS) as a functional cooking pot in their classes. BOSS teaches skills like fire making, flintknapping and hide tanning, which students use on extended trips into the desert backcountry. BOSS invited Olsen to teach a pottery course, and within two years, he was a head instructor and could replicate a variety of artifacts.

In the 1990s, new Utah laws required that archaeological collections be housed in a climate-controlled environment. Glen Canyon National Recreation Area’s artifacts were housed in simple glass cases at Anasazi Restaurant. The U.S. National Park Service hired Olsen to create replicas, which would remain on public display – this assignment unknowingly put Olsen in the crosshairs of a sting operation.

He was foraging materials near Zion National Park. When he got back to his car, he noticed it was surrounded by several government vehicles and one very nervous Bureau of Land Management ranger.

“I looked up where I just came from, and there were people running down the ridges in camo gear with riot shotguns,” Olsen said. The woman in charge of the sting was the undercover agent.

She started interrogating Olsen on the spot. “She said, ‘We know what you’re doing up there, you’re digging pots. And you have an accomplice up there with you, we heard you talking.’ ”

The agent had also seen what was in Olsen’s car: ancient-looking arrowheads, baskets and a black-on-white Anasazi pot. He’d made the whole cache, but they accused Olsen of being an illegal artifact hunter.

After three hours of interrogation, Olsen realized he could exonerate himself with a postcard that featured the black-on-white pot, a “sunflower bowl” from a well-known collection. He remembers delivering the coup de gras: “Do you really think I bought a post card and then went hiking up the canyon to find a pot that looked exactly like it?”

Olsen’s pots are often mistaken for antiquities, which is no small feat. “A lot of replicators make pots overly perfect so that when you handle it, there’s something lacking,” Ward said. “A prehistoric pot is slightly wonky, maybe a little asymmetrical, not quite as perfect.”

Olsen’s pottery is purposefully imperfect – and often slightly used.

Chris Hanson, the museum director at Edge of the Cedars, has seen Olsen make a pot one day, paint it and dry it the next, then serve food out of it to guests a few days later. “Using it gives the pot a character that others don’t have.”

The twist is that Olsen has occasionally found his own pots in black market catalogs. Unscrupulous sellers file off his signature and offer the pieces as genuine artifacts. Buyers can’t tell the difference. Olsen said he doesn’t feel sorry when those willing to buy undocumented pieces on the black market get ripped off.

Like his pots, Olsen has a distinct character. “A lot of potters are very secretive, but John is always so open with everybody,” Ward said. “If you want to learn, he’ll say, ‘Come over and I’ll show you how to do it.’ It has given him a reputation all around the Southwest.”

Olsen often shrugs off his accomplishments, as though rediscovering an ancient pottery technique was inevitable. And maybe for him, it was. “I always wanted to do this primitive stuff,” he said. “Trying to figure things out is kinda my deal.”

Look for annual pottery workshops at Edge of the Cedars Museum in Blanding, Anasazi State Park Museum or the Elkhorn Earth Skills Gathering, both in Boulder. Many classes are taught by Olsen’s protégé, Kelly Magleby, whose work can be found at kayentafire.com.