At the trail register into Robbers' Roost Canyon – a several-hundred-mile complex of towering walls and deep slots in remote southern Utah – a backpacker had scrawled a warning. A cougar came into his camp at night, yellow-eyed and prowling, and the hiker, "badly spooked," stayed up throwing rocks to keep the animal at bay. My friend Travis, a wisecracking Texan in his fifties, scoffed at the backpacker's note. "What would Butch have done?" he said, holding up the .380 pistol he'd brought with him. He meant Butch Cassidy – the real one, not the Hollywood version made famous by Paul Newman in the 1969 movie 'Butch Cassidy and the Sundance Kid.' In the 1890s, Cassidy and his band of merry psychopaths, the Wild Bunch, holed up in the Roost, one of the wilderness hideouts along the 2,000-mile length of what was known as the Outlaw Trail, the redoubt of the most successful bank and train robbers in the Wild West. "Couple rounds from this and a shot or two of whiskey," said Travis, "and we'll be fine."

A week earlier, in Grand Junction, Colorado, Travis had been accosted by a meth head, and he had drunkenly pulled a knife to defend himself. The guy backed off, but Travis made the mistake of sheathing the weapon, at which point the meth head decked him. Now his right eye socket and cheekbone, both broken, looked like they'd been smeared with tar. I'd wondered if he'd want to do the trip in that condition – he could barely see out of the busted eye – but with Butch Cassidy as motivation, he'd decided to man up.

Originally, I had wanted to use horses to trace the Utah portion of the Outlaw Trail, which is in fact a network of paths sprawling from Texas to Montana. Horse and cattle thieves during the 1860s were the first to blaze these byways, decades before Cassidy. In Utah, outcast Mormons wanted for murder or polygamy established some of the first settlements along the trail's most remote parts. But it was April, and the days were already hot, and no horse guide would take us into the Roost this time of year, as good water would be hard to find. So we shouldered our heavy packs under the sun, in a spring wind that stung our eyes, and headed out on foot.

That night, we camped at the bottom of the Roost, near the Dirty Devil River, which runs wide and shallow, silted and undrinkable. Our canteens were running low, the desert night was cold, and I kept thinking of the cougar. "Yep, that old mountain lion's watching us right now, got 10 times our night vision," said Travis, before drifting into a grinding snore.

In 1976, Robert Redford, who plays the Sundance Kid in the movie, traveled the trail for several hundred miles as part of an article he authored for 'National Geographic.' "As technology thrusts us relentlessly into the future, I find myself, perversely, more interested in the past," Redford wrote. "We seem to have lost something – something vital, something of individuality and passion. That may be why we tend to view the western outlaw, rightly or not, as a romantic figure."

Edward Abbey, environmentalist and self-described anarchist, who joined Redford on his ride along the Outlaw Trail, once wrote that the deserts of the American Southwest were a safe house of political liberty, "a refuge from authoritarian government." In his 1968 book, 'Desert Solitaire,' he described "revolutionaries, operating in mountain, desert, and jungle hinterlands with the active or tacit support of a thinly dispersed population." He was thinking of Vietnam and Cuba, but his words could equally apply to Butch and the Wild Bunch, who were able to survive because of the support of the Utah locals. "If guns are outlawed," Abbey continued, "only the government will have guns...and a few outlaws. I intend to be among the outlaws."

Once upon a time in America, a man could point a gun at a banker and flee with his money into the wilderness and not get caught. Renegades like Cassidy found their way on the Outlaw Trail, operating across terrain that remains even today some of the most forbidding in America. They survived – they thrived – because it was dangerous, unmapped territory. My idea, probably a foolish one, was to see if I could find a place in the wild reaches of the American West where an outlaw, or at least someone who wanted to feel like one, could still hide out.What we know of Butch Cassidy is as much fable as fact, and those who keep the history have often not been much interested in separating the two. It doesn't help that Hollywood's version of the story, with Newman and Redford carrying the banner of half-truth, is the one most people recognize. We do know that Butch Cassidy was born Robert LeRoy Parker, in 1866, in Beaver, Utah, the eldest son of Mormon parents. Growing up poor, Parker, at age 14, went to work on a ranch in Circle Valley, north of what is today Bryce Canyon National Park. There he met Mike Cassidy, a small-time rustler who was influential enough that Robert took his last name. Rustling was one of the only ways small ranchers and cowboys could survive in this era, as cattle corporations and barons had seized the best range. Utah author Charles Kelly, Butch Cassidy's earliest biographer, wrote in his 1938 book, 'The Outlaw Trail,' that when the barons "succeeded in squeezing out or running off a homesteader or small rancher by force, as often occurred, they frequently created an outlaw. Not being able to defend himself otherwise, the victim retaliated in the only way he knew how – by turning cattle thief."

Butch ended up running lots of stolen stock into the badlands of Bryce Canyon, into the stony wilderness of the Robbers' Roost, and beyond – into southwestern Colorado, through the tough cow towns of Mancos and Dolores and Cortez. Under Mike Cassidy's tutelage, he learned to ride bareback, rope steers, plant a hot brand, and handle guns. He learned the fast draw and how to make a standing leap into a moving saddle.

He soon drifted into Wyoming, Montana, and Nebraska, cowpunching on ranches for a meager living, and by 1889 he was in the mining boomtown of Telluride, Colorado. There he trained horses, hauled ore in treacherous horse trains, and became known as a skilled jockey in the horse-racing and gambling rackets that were the chief entertainment of cowboys. According to Charles Kelly, he was a well-built and charming young man, with "a disarming smile" and a "rapid-fire way of talking, which later served him well." He was "universally liked" and known across Utah as "the best shot in Circle Valley," this despite the fact that we are told in varying accounts that he abhorred bloodshed, was "never vengeful," "was quiet and inoffensive," and "cared not at all for liquor or cards."

In Telluride, he met a horse-racing buff and cattle rustler named Matt Warner, who one day persuaded him to fire a tremendously powerful gun while seated on a horse-watering trough. The gun – which Warner had, for reasons lost to history, nicknamed Butch – knocked young Cassidy flat into the water in the trough. To honor the occasion, he took the name of the gun, and Butch Cassidy was born.

Butch's first large robbery that we know of, in 1889, netted $21,000 from the San Miguel Valley Bank in Telluride, which he took down with Warner and two criminal associates. Chased by the law, he headed for the Outlaw Trail, fleeing west to Utah and then forcing his horse on a grueling 200-mile ride north toward the Wyoming border. After a rest of just three days, he doubled back, heading to the safety of the Robbers' Roost, which was already well established as a hideout for horse thieves and murderers.

By 1896, after having been caught near Lander, Wyoming, and then doing two years in state prison for horse theft, Butch had formed around him the core of veteran robbers and bad men who would eventually come to be known as the Wild Bunch – and sometimes as the Hole-in-the-Wall Gang and sometimes as the Train Robbers' Syndicate. It was a loosely run outfit. "There was no compulsory drafting of men into projects," writes historian Michael Rutter. "You worked if it suited you and you liked the job." Along with Matt Warner, Cassidy's band included William Ellsworth "Elzy" Lay, a cowboy intellectual who is said to have read history by firelight, and with whom Butch planned and executed some of his most difficult robberies; William "News" Carver, a sometime member of the murderous "Black Jack" Ketchum Gang, who enjoyed seeing his name in print; and Harvey "Kid Curry" Logan, described in most accounts as a cold-blooded murderer who was more feared than Butch Cassidy.

Somewhere along the way, Butch met up with a transplanted easterner from outside Philadelphia named Harry Alonzo Longabaugh, who had studied Shakespeare as a teenager and come west at age 15. In 1887, Longabaugh faced 18 months in jail in Sundance, Wyoming, after being charged with stealing a gun, a saddle, and a horse. He wrote a letter to the local paper "to set my case before the public in a true light....I have always worked for an honest living," said the man who would come to be known as the Sundance Kid, "but having got discharged last winter, went to the Black Hills to seek employment – which I could not get....After this my course of outlawry commenced." (The friendship between Butch and Sundance was exaggerated; most researchers agree that they committed, at most, three robberies together.)

And so began the short, sweet heyday of the Wild Bunch. In August 1896, Butch and Elzy Lay hit the Bank of Montpelier in Montpelier, Idaho, for $7,165 in cash, gold, and silver. A posse chased them for a week, giving up only after the outlaws vanished into the desert. In April 1897, they snatched at least $8,000 from the mine payroll at Castle Gate, Utah. 'The Salt Lake Tribune' declared the robbery – mounted by Butch and Elzy in broad daylight, in a narrow canyon settlement with only one point of egress – "one of the most daring affairs ever recorded." Butch holed up with his haul for three months in the Robbers' Roost, where he was now considered, as Kelly writes, "king of the Roosters, an aristocrat among mere cattle rustlers." When supplies ran low, Butch dispatched his women – hookers for the most part – to the lonely towns nearby for booze and bullets, sending them across miles of hard, waterless desert. Butch lived well in the Roost: He built tents and held big barbecues, all-night gambling sessions, pistol competitions, and horse races.

Between 1897 and 1900, Butch led or helped plan nearly a dozen major bank and train holdups. The assaults on the express-car caches of the Union Pacific Corporation made him infamous nationwide. 'The New York Herald', in 1899, described him as the leader of "lawless men who have lived long in the crags and become like eagles." He was hunted by U.S. Marshals, the Pinkerton Detective Agency, and Union Pacific mercenaries. Over the 10 years it was active, the Wild Bunch made off with roughly $200,000, the equivalent today of more than $4 mil­lion. They also committed at least 20 homicides, though Butch was never implicated in pulling the trigger. "I never robbed an individual – only banks and railroads that have been robbing the people for years," Butch told a lawyer friend in 1899. Charley Gibbons, owner of a general store in the Utah village of Hanksville during the 1890s, said Butch always paid his debts and "always paid cash." Kelly, in 'The Outlaw Trail,' wrote "all old-timers interviewed for this biography, including the officers who hunted him, were unanimous in saying, 'Butch Cassidy was one of the finest men I ever knew.'" Butch was Robin Hood with a Colt .45, and enough sources attest to his decency streak that it might even be true.After two days on the trail, Travis and I made for the highest reaches of the canyons of the Roost, where that hiker had encountered a cougar and where we hoped to find some evidence of Butch or the Wild Bunch in the caves. It was a hellacious slog. The sun bashed down on the canyon floor, the walls heated up in a furnace effect, and the trail was nothing more than deep, wallowing sand.

Soon we were parched and needed more water. Butch, who understood this land better than just about anyone, had fewer problems. He knew the springs and secret seeps that kept him one step ahead of lawmen, who feared they'd die of thirst if they chased him into the Roost. After an hour of hunting around and cursing, we finally came across a seep under a cliff furred with supple vegetation. It dripped as slowly as a stopped clock, and we spent another hour in the sun, battling the gnats, to gather one liter of the precious stuff. At one point, I thought I heard the voices of other people coming to the spring for water. "We'll have to fight 'em for it," said Travis, practicing his Texan tough-guy twang. No one appeared, but Travis still drew the pistol and fired 50 rounds into the ground, the reports launching against the canyon walls. The gigantic silence squelched the last of the shots, and we ate canned sardines and couscous for lunch, with an aftertaste of dirt. We never found the caves.The goal, after three more days of wandering in the canyon, was to head east in our rented Jeep on the miles of intestine-bashing road that skirt the Roost, following, as best we could, the Outlaw Trail toward Horseshoe Canyon, the site of another of Butch's camps (we never found that one, either). Not far from Horseshoe, we came upon a group of six half-lost college kids straggling along a dirt road in shorts and T-shirts, their eyes ringed, their faces hangdog. They had gone too deep on a canyoneering expedition, couldn't find the exit as the daylight waned, and were forced to spend the night in the canyon, unprepared, with no survival gear. Only a few miles away was the spot where canyoneer Aron Ralston famously trapped his arm under a chockstone and then amputated it below the elbow. Ralston's story is captured in a movie, '127 Hours,' although given the choice I'd rather have Paul Newman than James Franco play me.

We gave the kids water from the five-gallon jug in the back of our Jeep. Travis shook his head as they plodded away. In every direction, there was cliff, canyon, sand, rock, and no shade worth dying in. We were five hours by   from the nearest outpost of civilization. "The view from the summit of the Roost country," as Kelly put it, "is either sublime or depressing, depending on the amount of water in one's canteen." Travis' assessment was toward the depressing. "Anything goes wrong – get hurt, get sick, horse goes down – you're screwed. A wounded man out here is a dead man." Later, we sat around the campfire and muttered over the dregs of the whiskey. "Know what those old-time sheriffs needed in the Roost?" said Travis finally. "Hellfire drones. Outlaw is sitting in his little canyon, got his Old Crow in his tin cup, horses are happy, he thinks he's got it made – whoosh! Boom! You're dead!"

A few days later, Travis went home, and I moved on to another vast wilderness in Utah called the Book Cliffs. It was 60 miles north of the Robbers' Roost but only a day's ride or less for a horseman like Butch, who once claimed he rode a horse 110 miles in 10 hours. "The fact is that Butch...had made some of the most demanding rides ever known," wrote author and horse guide Simon Casson, "with the added pressure to outpace pursuit, avoid ambush, and evade capture." The astounding horsemanship of the Wild Bunch was key to their success as thieves in the American wilderness.

I was joined by a 66-year-old veteran horse packer from Colorado named Ronni Egan, who runs a conservation nonprofit called Great Old Broads for Wilderness. As a young woman, Egan worked for the legendary packer A.C. Ekker, who, during the 1980s and 1990s, maintained a ranch at Crow Seep in the Robbers' Roost, one of the springs where Butch watered his horses. We rode in Egan's truck past the town of Green River, where the Wild Bunch often resupplied, and through the abandoned mining village of Sego, where Butch and Elzy Lay stopped in 1897 while driving a string of "fine horses." Beyond the seemingly impassable line of cliffs was the East Tavaputs Plateau, a folded country of high-altitude canyons and forested ridges. The Outlaw Trail, where it passed into the cliffs and over the Tavaputs, was once a major line of transit for cattle and people, connecting the Roost country with another redoubt on the trail known as Brown's Hole, 150 miles to the north.

The road turned to rough dirt and cobbles, rising 3,000 feet through the cliffs into the high country. A friend of Egan's named Dana Ivers was waiting for us at a campsite at 8,500 feet, under tall pines and with a hundred-mile view south across the Roost and beyond. Ivers, who is 62, was tiny and quick-footed and had a cackling laugh.

The fourth member of our party was Travis Buck, a 29-year-old ranch hand from Colorado who would serve as horse wrangler on the expedition. Buck was tall and bone thin, had shining blue eyes, and wore a wide Stetson and a torn leather vest, over which hung a 9mm pistol in a shoulder holster. When we arrived, he was tending to a line of five horses picketed between pine trees, brushing them down, looking for burrs. The pistol was in case he'd have to shoot one of them if it broke a leg.

In the morning, we headed out under grim, cold skies with provisions for a night and two days, the goal to follow the trail 20 miles or so into a roadless wilderness full of elk and cougar and bear. "Back in the outlaw days," said Ivers, "this was the middle of nowhere."

"It's still the middle of nowhere," said Egan.

Buck said he smelled the musk of elk in the distance as we rode, and sure enough, we spotted a herd on a ridge not far away. We had six dogs with us – collies, an Akita, a Scottish terrier – and they took off like rifle shots, giving chase as the elk thundered in flight. Our horses ignored the commotion, plodding dutifully, and when the dogs came back empty-mouthed and sad-eyed, the steeds slapped them off the path.

Egan rode Jim, a sorrel quarter horse that stood 16 hands tall, the alpha of the herd. He was "broncky," as horsemen like to say, tossing his head, fighting the reins, ignoring commands, and threatening to shrug Egan off his back. Buck was on Diablo, a cranky Appaloosa gelding who got his name a few years back when he spooked and charged, wrapping Buck's testicles on the saddle horn. Ivers had taken Tailstar, a.k.a. "The Professor," a thoughtful Tennessee walking horse. I was given Ironfoot, a palomino said to be "good with children."After riding four slow hours over a trail through the woods and atop the ridges, stiff in the ass, knees on fire – sometimes vice versa – I was happy to make camp in a narrow vale that Buck had chosen for its supply of rich spring grass. Night fell, a fire blazed, beers were opened, buffalo steaks were set on a grill. We talked about racehorses and lazy horses and outlaw horses – horses that refused to be trained. "Horses don't love us," said Egan. "They love each other. Where's the oats? That's what they're asking. You show up every day with grain and treats, then they'll love you."

Buck nodded. "You know a dog will stay with you if you're dying. A horse won't," he said. The cowboy-outlaws, Egan said, who used and discarded their mounts as necessary, treated horses the way they should be treated. "People want to make horses into pets, into dogs," she said. "They're just big, dumb livestock who are very useful."

We talked about Butch. Buck liked what Butch stood for. He told the story of how Butch gave $500 to an old rancher couple to pay a banker threatening them with foreclosure. (When the debt was satisfied, Butch found the banker and stole back his money.) Or how he stopped hard in the middle of a chase, a posse close behind, to give away a white horse he'd promised to a wide-eyed boy on a ranch in Nevada.

"Butch was sick of seeing the big cattlemen, the rich people, taking from the lower classes," said Buck. "He was fightin' an unfair system, fightin' for the little guy. Yes, he was a criminal, he was a fugitive, but he didn't do so much wrong." Buck, too, shared the belief that Butch had never killed anyone. "Never hurt a man – I still think that's pretty neat," he said.

Buck unfurled his bedroll close to the horses that night. Jim, the alpha, had attempted an escape at dusk, so Buck was watchful. He told me later that it had been a long time – many months – since he had slept in the open, and it made him happy. This reminded me of something Charles Kelly had written about Butch and the Wild Bunch, how they "hated the monotony of settled communities. Their greatest joy was found in exploring new country, camping in the desert, and telling tall tales around a campfire."By 1900, technology was at the heels of the Wild Bunch: the expanding network of telegraph wires; the invention of the telephone; the new paving of roads; the high-speed locomotives, outfitted to move a posse most anywhere needed. The renegades fell one by one. Elzy Lay, Butch's smartest man in the saddle, was caught and given a life sentence. Matt Warner did two years in a penitentiary and went straight. The "Black Jack" Ketchum Gang was decimated, its members killed or dispersed. News Carver was killed; Harvey "Kid Curry" Logan, cornered by a posse near Rifle, Colorado, shot himself instead of being taken alive.

Foreseeing a dismal future in the U.S., Butch fled, in 1901, to South America, accompanied by the Sundance Kid and Sundance's girlfriend, Etta Place, who was described in Pinkerton files as "a refined type." Etta may have been a schoolteacher, but she may also have been a prostitute. In Argentina, planning to go straight for good, the group started a ranch. By 1906, however, Etta disappears from the history, and Butch and Sundance leave the ranch and become outlaws once again.

Two years later, after robbing a mine payroll near San Vicente, Bolivia, they were surrounded by soldiers and killed in a bloody gun battle. One version of their deaths – there are many – relates that Butch shot the dying Sundance with a bullet to the head before turning the pistol on himself.

Yet there were also rumors that Butch returned to the States without Sundance sometime after 1908, changed his name, went on to start a number of manufacturing businesses – among them, a company that made, of all things, counting machines – and that one day in 1925, he showed up in Circle Valley to visit his family, driving a shiny new black Ford. Bill Betenson, Butch's great-grandnephew, believes this is the real story. "The two men killed at San Vicente were buried as unknowns," Betenson told me. "They were never identified. And the grave site has never been found. To me, there are still a lot of questions."On my last day on the Outlaw Trail, Buck took me out alone, he on Jim, me on Ironfoot, trotting along a path through tumbled ridges. "You said you wanted to gallop – well, you wanna?" He tapped Jim's flanks with his boots, shook out the reins, and shouted, "Hyah!" Jim shot away, Ironfoot following, and for two minutes that felt like a long death, we galloped. I rose in my stirrups, realized this was exactly the wrong move, and felt my body shifting off the saddle, saw the fall coming: my ankle broken, skull cracked, the sun blotted, teeth and nose and eyes shredded in sharpened dirt. I gripped the saddle with my thighs, hunkered my frame, and held on. It was terrifying and awful and beautiful, the surging of the horse like a series of electric shocks fired up my legs and spine and out the top of my head.

Later that day, after we made it back to camp and the horses were turned out in the grass, Jim led an escape with Tailstar in tow, and we could not find them. Buck called and called. Ironfoot and Diablo stood at the picket line under the pines, whinnying, stamping their feet, longing for the security of the herd. Buck ran to his truck, and with Dana Ivers and me, tore out to the jeep road. They found a trace in the sand leading from the Tavaputs and out of the Book Cliffs, south toward Colorado. "Goddamn, they think they're going home," said Ivers.

Six miles down the road, on the dizzying descent out of the Book Cliffs, was a cattle guard where the horses could get caught and break their legs, which would mean they'd have to be killed on the spot. Buck sped the truck along the twisty road, looking for evidence of passage: the snaking line of the halter ropes, then a pile of fresh manure, then hoof tracks. It was late afternoon, the light blue and dank as the sun failed over the ridges.

Finally, we spied the horses jogging in the distance. At the sound of our engine, they turned to look, and as if caught in a crime, they shook their manes and ran faster.

Ivers took the wheel, and Buck bounded from the truck. In a single, running, catlike leap he was on Jim's saddleless back, high on the animal's withers, legs splayed, his left hand gripping the mane. He grabbed the halter line that still held Tailstar and wheeled both animals around and grinned. "You turds," he told the horses. "He's got it," was all Ivers said as we sped back up the hill in the truck.

A few minutes later, we stopped at an overlook, waiting for Buck, worried now because he hadn't followed. From the perch, I could see the entirety of the Robbers' Roost where Travis and I had backpacked and been thirsty and wanted out. "We need these places like we need air," Travis had said. "A free man can't live in the termite existence of the cities. If you're gonna rebel, you need wilderness."

Travis told me later that I should "romanticize the hell out of our trip," that if this were a cowboy tale, we'd have met the cougar in the Roost and roped him, discovered a slug from Butch's gun, walked 50 miles with no water. Instead, there was only the silence of the country, the unspeakable enormity of it, the distant plateaus, the perilous deserts, the impossible canyons. Unlike in Butch's day, though, this space had been mapped. We were only a couple of hours from Grand Junction. Ivers had a signal on her cellphone. If anything went wrong, we could call in our location, and the Hellfire drones would be on their way.

Three thousand feet below us, I was scheduled the next day to meet an environmental activist who had told me there were plans to develop the East Tavaputs. Rich veins of oil-shale and tar-sand deposits waited to be exploited. The area would be ploughed under with new roads, the forests felled, the streams fouled, the wilderness strip-mined. I wondered what Butch would make of this: a tragedy or an outlaw's opportunity? I suppose it would depend on where they kept the payroll.

"See him?" Ivers said. I did not, but I heard the hooves. Buck was nearby, galloping the horses up the road. Ivers and I stood on the perch and listened. The sun, disappearing in the west, stained the land shades of sepia. There was a sweetness and melancholy to the fading light, and the hooves clattered and echoed. "There," she said. Around the bend came Buck, riding bareback, fast and head forward, and I swear he was a figure out of myth.