This 210- to 220-mile, 20- to 30-day cross-country journey could be the premier mountain trek in the Lower 48. But it is an expert route—not for novices, youth groups, bad knees, or even experienced trail hikers new to loaded scrambling and off-trail navigation.You’ll hop boulders for 40 miles, and cross a sawtoothed succession of steep passes and deep gorges. You’ll traverse two national parks, three wilderness areas, one national monument, 33 named passes, and 11 major divides. If you’re unsure of your abilities, gain experience on less committing trips or section-hike the route. Since this trek crosses much fragile alpine tundra, smallgroups and Leave No Trace practices are mandatory.