He has ascended over 50 peaks in the Sierra Nevada as well as many summits in the French Alps.

Mark encountered a freak accident on a descent in the John Muir Wilderness in 1982, which left him a paraplegic.

Continuing his passion for climbing, in 1989, with climbing partner Mike Corbett, Mark made history as the first paraplegic to ascend the 3,000 foot face of El Capitan in Yosemite National Park, and in 1991, conquered Yosemite's other big wall, Half Dome.

A former member of the United States Disabled Ski Team, competing in two Paralympics, Mark is also know for his extreme downhill skiing and whitewater kayaking adventures.

In the spring of 1993, Mark skied 50 miles to be the first paraplegic, unassisted, to sit-ski across the 10,000 foot Tioga Pass in the Sierra Nevada Mountains.

From 1986-1991, Mark worked as a full time Interpretive Ranger and as Director of the Disabled Access Program in Yosemite National Park.
In 1996, honored by the Paralympic Committee, Mark ascended a 120-foot rope with the flaming torch to light the Olympic Cauldron.

His autobiography is titled Climbing Back. He has designed adaptive equipment and has developed programs to inspire and motivate others, including films highlighting a variety of athletes with disabilites.

He speaks for Disabled Sports USA, and lends his name to the Governor's Committee on Employment for the Disabled.
He has received numerous awards, such as The 1989 Senate Resolution, Arete Ward, Timpany Center Award, American Red Cross Summit, National Athletic Awards and the FDR Award for Courage in Sports.