MY MAIN DUSTUP WITH Lowe happened in 1999, when we were planning a trip to the Himalayas with Dave Sheldon. Our objective was the Sharksfin, a technical 21,850-foot peak in India that Sheldon and I had attempted a year earlier. It seemed like a dream plan—a great route, a legendary climber, and a pair of eager youngsters ready to make it big.

I trusted everything about Lowe except his reputation with other people's money. Two weeks before our departure, he called, citing "cash flow" issues and fishing for an airfare loan. At first I agreed, but after looking at my own skimpy bank account, I called back and, with great trepidation, removed him from the team. Lowe sounded calm, even slightly relieved. But two hours later he called back to rant at me for being "a fucking egomaniac," unwilling to share the glory.

Truth be told, a hidden part of me craved the glory of a great first ascent, which Lowe's long shadow threatened to obscure. But money was the bottom-line issue, and my decision drove a wedge in our relationship. In the end, the expedition was a failure, and Lowe discovered he had a bigger problem: Later in 1999 he began to experience the chronic pain, loss of coordination, and fatigue that, by 2001, would be formally diagnosed as MS.

We patched up the feud in later years, and it seemed frivolous and remote when Lowe picked me up at the Salt Lake City airport. Now a few inches shy of his old, ramrod-straight height of five-ten, he was hunched over two canes. Though he can barely walk, he can still drive. During the 40-mile trip to and through Ogden, he braked hard, accelerated harder, and zipped around to show me a few local crags. After a slightly terrifying 60 minutes, we reached the six-bedroom brick rambler where he grew up. He bought the house from his siblings after his mother, Elgene, died in 2006.

Lowe's office was a long rectangular space toward the back of the house. Bookshelves and file cabinets bulged with guidebooks and alpine journals. The light table in the far corner was stacked with slide sleeves. I thumbed through past glories: Lowe in the Tetons in the late sixties; Lowe and David Breashears on a dramatic peak called Kwangde in 1982; a sinewy, ripped Lowe in his early twenties, shirtless and bouldering. It was an amazing collection of historic climbing photography.

A stone's throw up the road was a gated trailhead marking a path to the base of a blocky, half-mile-wide quartzite wall. On those walls and on the boulders scattered below, the Lowe clan—four boys and four girls—learned how to climb. In 1967, Greg free-climbed a route on the backyard crag that nobody repeated for 35 years. (Free climbing means using gear for protection only, not as a support or means of progress.) At 5.12b/c, it was then the hardest free climb in the world.

"Mom would pack our lunch and send us off with no supervision," Lowe said. "There were enough of us so that if she lost a few, there would still be plenty left."

Elgene was a classic 1950s housewife and a rare Lutheran living in Mormon Utah. Lowe's father, Ralph, was a Pacific Theater bomber pilot in World War II who rejected his Latter-day Saints upbringing and declared himself an atheist. Later he earned a law degree, eventually becoming an assistant DA for Ogden's Weber County. Ralph's work ethic led to a heart attack that killed him at age 65. This hard-driving example left a mark on the Lowe kids. Lowe tells me that their sibling rivalry "often resembled an episode of Dallas."

Not all of them could handle the pressure. In 2001, Lowe's younger brother, Kim, died of a drug overdose. "Kim was an alcoholic," Lowe says. "He was trying to live up to everyone's expectations."

Lowe was, too, and he set a high bar for himself. Smaller than his brothers, he had to be tough just to keep up. His climb of Telluride's Bridal Veil Falls in 1974, followed by his ascent, at 23, of the technical north face of 19,400-foot Peak 19, in what is now the Central Asian republic of Tajikistan, hinted at an emerging greatness. With these, and a score of standard-setting climbs in the Canadian Rockies, Lowe introduced a new level of difficulty to the al­pine world. He combined exploits in the Andes with several landmark climbs in the Himalayas. His 1978 attempt on the north ridge of Pakistan's Latok I—a dramatic 23,443-foot peak where he, his cousin George, Jim Donini, and Michael Kennedy were turned back 500 feet from the summit—remains unmatched three decades later. After some two dozen attempts, nobody has come close to their high point.

The next year, solo and unroped, Lowe took on the south face of Nepal's 22,494-foot Ama Dablam. The 4,500-foot route—taller than any other ice climb of that era—demanded tough climbing on sketchy ice at high altitude. It was the first solo first ascent of that magnitude in the Himalayas.

On Everest in 1981, Lowe joined one of his few formal, siege-style expeditions. He didn't summit and says he was turned off by "the groupthink, politics, and vaguely militaristic feel." From then on, he kept pursuing trips on aesthetically pleasing and difficult objectives. In 1994, he revolutionized ice climbing with an ascent of a route called Octopussy, in Vail, Colorado. In his mid-forties, a still-spry Lowe pulled through the horizontal rock roof and dripping ice fangs, often pitched upside down in a gymnastic pretzel position called a figure four. Mixed climbing, which simultaneously takes you through rock, ice, and snow in a creative hybrid of movement, tools, and techniques, was as old as mountaineering itself. But no one had ever fused outrageous terrain with such a wild blend of traditional technique and new-wave sport-climbing moves.

Will Gadd, now one of the best mixed climbers around, remembers seeing pictures of the route while in his late twenties and going straight out to buy a new set of ice tools. "The shots of Jeff on Octopussy changed my mind-set about winter climbing," says Gadd. "A whole new world was suddenly wide-open. It was like falling in love with a supermodel."