“We are now ready to start on our way down the great unknown. We are three quarters of a mile into the depths of the earth, and the great river shrinks into insignificance as it dashes its angry waves against the walls and cliffs that rise to the world above… We have an unknown distance yet to run, an unknown river to explore.” —excerpt from “The Exploration of the Colorado River and Its Canyons,” by John Wesley Powell

In 1869, John Wesley Powell, a one-armed former soldier, geologist, and explorer, set off on what would be one of the most iconic journeys in the American West. The eponymous expedition, a three-month river trip down the Green and Colorado rivers, began at Green River Station, Wyoming, on May 24, 1869 with 10 men in four small boats; on August 5, Powell entered the Grand Canyon, with one fewer boat and three fewer men. It was the first official U.S. government-sponsored passage through the Grand Canyon.

One hundred and fifty years later, a group of 14 guests is embarking on a 28-day journey retracing what is now known as the Powell Geographic Expedition. An additional six will make the first half of the trip before switching out with six other guests, who will finish at the old location of Cass Hite’s Ferry, which was flooded by Lake Powell. It’s a lofty pursuit, one that took months of planning and organization to pull off.

It’s a trip that George Wendt, the now-deceased founder of OARS, a California-based water expedition company, long dreamt of. Wendt was a Powell enthusiast/historian; he even participated in film projects in the ‘90s that involved river guides in costumes and retraced legs of the journey. Wendt passed away in 2016, but the passion remains alive among OARS river guides—especially anniversary trip leader, Lars Haarr. The expedition is also one that OARS is uniquely qualified to take: It’s the only outfitter with permits for the different stretches along the route.

“This is something that I’ve been thinking about for a long time,” Haarr said. “When I moved to Moab in 1999, I got interested in John Wesley Powell and read excerpts from his book on my trips and talked about the odds that these guys faced then … I had thought: ‘Hey, it would be cool if you kind of retraced his trip a little bit.’ With the anniversary of John Wesley Powell doing his trip and OARS’s 50th anniversary, it all just came together.”

The trip starts at Flaming Gorge Canyon in Wyoming, entering Dinosaur National Monument through the Gates of Lodore then running rapids through Split Mountain Canyon. In the Uinta Basin, rafters pass through Ouray National Wildlife Refuge before arriving at Sand Wash and Desolation Canyon—this is the halfway point. From there, the river winds through more dramatic canyons with evocative names like Labyrinth, Stillwater and Cataract before ending at the old Cass Hite’s Ferry.

Of course, today’s guests won’t encounter the hardships that Powell’s expedition faced: the food is gourmet, the sleeping pads are plush and the chances of mishaps are severely limited due to the expertise of the guides. But the wide swaths of the Milky Way that are visible on a clear night, the sound of the river as you fall asleep and the adventure—especially the adventure—are magical.

“(The) idea of a journey into the great unknown is alive and well, for anybody that does a river trip today,” said Steve Markle, vice president of sales and marketing for OARS. “Whether it’s a three-day river trip or a 28-day river trip…you’re out of your comfort zone. It’s just really kind of a unique, and I’ll even say magical, experience for people.”

Though the 28-day full expedition launched on June 5, there are still opportunities for those who want to recreate part of Powell’s trip. The lower section, from Sand Wash to Hite, leaves on June 17. There are also fall trips (7, 12 and 18 days) that depart in September. There are also shorter trips that share the beauty that Powell and his crew encountered.

“I think that’s the draw for a lot of these folks in retracing the John Wesley Powell expedition—it was such an adventure,” Lars said. “It’s a way to touch a little bit of that unknown.”

If you go: Trips range from $99 for one day trips to $799 for the three-day Flaming Gorge trip and above; trips are all inclusive. Visit oars.com for more information.