LeConte loved mountaineering from the time he was a teenager and went all over the Sierra Nevada exploring, sometimes for several weeks. He produced the first map of the central Sierra Nevada for the Sierra Club, based on his exploration. At that time, USGS maps were not available. Along with James S. Hutchinson and Duncan McDuffie, he pioneered a high mountain route in 1908 from Yosemite National Park to Kings Canyon, roughly along the route of the modern John Muir Trail. In 28 days, they completed a trip of 228 miles through the high mountains, including several previously unexplored sections.