Disney's love of the outdoors and Rocky Mountain National Park (RMNP) grew from an early age when he spent his childhood in Glen Haven, just outside the park. From the age of 6 or 7 he would explore mountains and meadows and the only rule was that he be home for dinner. Over his lifetime he achieved over 1000 ascents to named and significant unnamed summits in the Western United States, Canada and Mexico, including Denali in Alaska. He summited the park's iconic 14,259-foot Longs Peak 93 times and all of the park's 128 named peaks at least once.

As a young man he worked as a climbing guide and later as a seasonal ranger in RMNP.

In 1996 he received the Environmental Stewardship Award from Rocky Mountain National Park for his work with citizens, and local, state and federal governments to permanently ban commercial sightseeing flights over the park.

Jim was an accomplished painter with a 50-year career. His work focused on mountains and western landscapes and has been displayed at galleries and museums throughout the country. He designed an ornament celebrating Rocky Mountain National Park that adorned the White House Christmas tree in 2007, was commissioned by the Rocky Mountain Conservancy to create a poster marking the park’s centennial and twice was the park's artist in residence.

“He showed us trails that only he knew about and sometimes recited poetry as we were hiking down,” said Betsy Mosehauer, president of the Loveland Mountain Club. “He could name every mountain in the Front Range and knew a lot of the history of (Rocky Mountain National Park). He lived a full life and left a rich legacy.”