On the day before we cross the divide,we hike up to a place where Sawchuk has never been—which is saying something. Sawchuk has spent years exploring the region on foot, horse, snowmobile, and snowshoes, but he'd never made it up to Gataga Pass. Then again, few people have. A handful of hardy local hunters, hunting guides with well-heeled clients, and helicopter-borne mineral prospectors are about the only visitors to these glacier-bound peaks. The view, once you get there, is on an IMAX or Grand Canyon scale. From the 6,000-foot saddle where we stand, the mountain falls away for thousands of feet into a lush, green valley that stretches southward for 15 miles before running into yet another phalanx of glacier-­clad mountains.

It's breathtaking, not just for its beauty, but for its sheer size; this enormous valley seems to have its own gravitational pull. All around us, the rush and roar of rivers being born thrums in our ears as glacier-fed waterfalls carve near-vertical paths down the mountainsides. Far below, the scars of winter's avalanches appear as great swaths of flattened trees. A moose cow and calf graze at the tree line while, high above, a dozen mountain goats trail across a precipitous scree slope, challenging the stability of its angle of repose.

What is so extraordinary about this wilderness is that one can follow these rivers and explore these ranges for days and weeks and never see a person, a rail line, or even a fire tower. This is the West as Lewis and Clark, or Roosevelt and Muir, might have seen it: a landscape without familiar reference points, where everything is so massive and raw that estimates of height and distance continually fall short of the reality. In the upper Gataga Valley we crossed a recent rockslide that could have buried a football stadium. In the upper Tetsa there are anonymous waterfalls with drops approaching a thousand feet.

The animals behave differently in here too, and it underscores a key distinction between places like national parks, where wild animals live but are habituated to human beings, garbage, and cars, and places like the M-K, where they are truly wild. Despite the fact that we encountered grizzly signs every day, including numerous kill sites, we never secured our food. To a seasoned outdoorsperson such behavior might seem irresponsible or even dangerous, but here humans are alien, to be avoided, and bears stayed away from our campsites. Only the mountain caribou (which travel in far smaller groups than their barren-ground cousins) were overcome by curiosity, and sometimes they would shadow us on the trail.