Washington Post News Service: In southern Sierra Nevada, California, an old man with an untamed beard hikes a familiar trail, his sinewy legs pumping like pistons for mile after mile towards an ideal and away from civilisation.

George Woodard is his name in the legal sense but he no longer is that person. On the trail he is known by his nom de guerre: Billy Goat.

"George is the name my mother gave me," he said.

Billy Goat has hiked more than 32,000 miles - which would have taken him around the world and a third of the way again.

He has walked across the South and the Southwest, the Northeast and the West. He has crossed the Rocky Mountains on four occasions, twice in each direction.

He has conquered the so-called triple crown of American hiking - the Appalachian Trail, the Continental Divide Trail and the Pacific Crest Trail - multiple times.

He has a wife, his third, and a home in Nevada. That is where George, the 69-year-old retired railroad worker, would live if Billy Goat cared to be George.

Billy Goat lives more than ten months of the year outdoors, drinking unfiltered water from streams, eating 8-ounce meals he prepares himself, sleeping under the stars without a tent.

He carries what he needs in a backpack weighing less than 10 pounds.

"I'm not on vacation. I'm not out for a weekend," he said, settling in for the night under a fire-scarred tree next to a gurgling creek and surrounded by the rugged granite outcroppings of the Dome Land Wilderness east of Bakersfield.

"This is where I live. When you do that, all the other trappings of life fade away."

For six months of the year, Billy Goat's home is the Pacific Crest Trail, the 2,650-mile uber-trail that stretches from Mexico to Canada through California, Oregon and Washington.

He is a legend in the small but growing fraternity of ultra-long-distance backpackers, renowned for his stamina and trail knowledge and envied for a single-minded devotion to living outdoors.

First-timers on the trail inevitably hear about Billy Goat. They spy his signature entry in trail-head logs - a red-ink stamp of a goat. Chance encounters are described in awed tones on internet journals.

Each year about 300 people try to hike the Pacific Crest Trail in one season, generally April to September. Of those, about 60 per cent make it - fewer than the number of people who scale Everest in a year.

It's a gruelling odyssey through the stratum of the American West. From broiling deserts near sea level to snow fields above 14,000 feet. Along rocky ridgelines and through rainforests. Across swift, frigid streams and plunging canyons.

Planning a Pacific Crest expedition takes longer than the journey itself.

Timing is everything: The desert must be crossed before it becomes dangerously hot, while the window for traversing the Sierra's snow is relatively narrow.

A steady pace must be kept - 20- to 25-mile days are the norm. Daily life is rendered primeval - food, water, shelter and miles are all that matter.

Small-town post offices and other resupply spots constitute stations of the cross for weary hikers.

The challenge is so engrossing that hikers shed their identities and adopt trail names. Tattoo Joe and Mr Wizard.

Bad Pack and Thunder. Dirty Bird, Numskull and Good to Go.

"You're going to be hot, cold, hungry, dirty, tired, sore all the time. Once you get past that, you're gold," said Jackie "Yogi" McDonnell, a 43-year-old waitress who has hiked the triple crown and wrote a trail guidebook. "Your body can do it. The challenge is mental."

Because of that, McDonnell knows it is impossible to predict a hiker's ability to complete the trail.

An athletic college student on summer break may not have the mental toughness of a 45-year-old who takes on the Pacific Crest Trail to exorcise a midlife crisis.

"You'll see Billy Goat and say: ‘No way, he's 69 - he can't make it,'" said McDonnell, who has hiked with him numerous times.

Indeed, at first glance Billy Goat looks as if he might have just emerged from a homeless shelter.

Twelve years ago, he was diagnosed with diabetes. But at 5-foot-7 and 150 pounds, there isn't an ounce of fat on him.

His shoulders are as square as a sawhorse from carrying a pack. His legs, scarred by innumerable cuts in the wild, are as taut as wire rope.

"He's an amazing man. Ask him: ‘Where do you live?' and he'll point to the ground and say: ‘Here,'" McDonnell said.

"He's so completely comfortable in his own skin. There's just an aura that surrounds him."

George Woodard grew up in northern Maine surrounded by poverty and the infinite outdoors that would become a respite for a troubled soul.

Woodard left home at 17. A poor student, he had no interest in college and sought a railroad job because it was steady and paid well.

Except for a stint in the army, he would work for more than 30 years as a conductor and yard foreman for a number of railroads.

"When I was in my 40s I was bound by my job," he said. "I would dream and fantasise about hiking all the time. And when I would finally go, I used every available moment. I would drive back just in time to go back to work."

The outdoors lifted his mood and silenced his anxieties. A roof over one's head was nothing more than a cage, he concluded.

Woodard lived frugally, stockpiled money and, at 50, retired and escaped into the woods. "We're only here for a short while. Time runs out on us," he said.

Over thousands of miles, Billy Goat has developed a Zen-like asceticism in which life is reduced to one dimension, a straight line towards an ever-receding goal.

Billy Goat has learned a great many things living outdoors. How to find water where there seemingly is none. How to utilise a cluster of boulders to hang food overnight out of the reach of bears.

How to navigate using a compass and map - a dying art in a world of global positioning devices, which Billy Goat would no sooner carry into the woods than he would a bowling ball.

He is obsessed with shedding every last unneeded ounce, a passion common among ultra-long-distance hikers. When travelling between trail heads, he would rather sleep in his car - a 1990 Toyota Tercel dubbed the Goatmobile - than a motel.

"The more you hike, the less you need," he said. "People always say: ‘What if? What if? What if?' I don't think we should be too consumed with what-ifs." Billy Goat's goal is "50 by 80" - 50,000 miles by the age of 80, more than 1,600 miles a year.

"The only thing he lives for is to be on the trail," his son, Toby, said. "When the point comes when he can't go out and walk a couple thousand miles - he's scared to death of it."

But not today. The sun is barely up and Billy Goat is adding to his internal pedometer, legs pumping like pistons up and over a ridgeline, each step taking him farther away from a man named George.