Kilian Jornet wanted to summit 72 of the tallest peaks in the contiguous United States. He gave himself a month to do it.

The Beginning Kilian Jornet was drenched and tired. Mr. Jornet, 37, was just a few days into an ambitious odyssey, a self-designed project he had named “States of Elevation.” His goal was to link, by foot and by bike, the tallest peaks in the contiguous United States — a series of 70-plus publicly accessible mountains in Colorado, California and Washington known as the “14ers” because they are all 14,000 feet or higher (symbolized on the map as ). He estimated it would take him around a month. But now, in early September, Mr. Jornet wondered whether he could continue. It is not often that Mr. Jornet, one of the most accomplished endurance athletes on the planet, seems susceptible to human frailties. In 2017, he reached the summit of Mount Everest twice in one week, without support or supplemental oxygen. In 2023, he climbed the 177 tallest peaks in the Pyrenees in eight days. Last year, he needed just 19 days to tackle the 82 tallest peaks in the Alps. But now, after a long flight from Norway, where he lives with his wife, Emelie Forsberg, a former skyrunning world champion, and their three young daughters, Mr. Jornet was jet-lagged and struggling to acclimate to the high altitude of the LA Freeway in Colorado, a mountainous traverse along the Continental Divide. Figuring out the correct gear was part of the puzzle when Kilian Jornet was planning his “States of Elevation” project. Nick Danielson Making matters worse, a steady rain left him feeling as if he were soaked through to his core. “I just felt exhausted,” Mr. Jornet recalled in a recent interview. “It felt impossible to do one more week, let alone another month.