The classic and most-traveled route up Montana's highest peak, climbing to Mystic Lake, crossing the alpine Froze-to-Death Plateau, and finishing on Granite's exposed East Ridge.
From the West Rosebud (Mystic Lake) Trailhead, a good trail climbs gently along West Rosebud Creek for about three miles to a dam overlook above Mystic Lake, gaining roughly 1,200 feet. The trail continues along the lake's south shore; about half a mile past the lake a junction with the Phantom Creek Trail branches left and switchbacks steeply up through timber to treeline, then climbs open slopes to the Froze-to-Death Plateau at around 11,000 feet. Once on the plateau, travel is cross-country over talus and tundra, heading southwest for several miles toward the Tempest-Granite saddle (Bivouac Saddle), a common high-camp location. Most parties break the approach into two or three days, camping either on the plateau itself or near Froze-to-Death Lake below its northern edge. From the saddle the route parallels the East Ridge on an intermittent climbers' trail through a large talus field known as "the Triangle," then works through sections of exposed Class 3-4 scrambling. The crux is a narrow, corniced snow arete sometimes called the "snowbridge," followed by ledges and short rock steps leading to the summit block.
Most parties reverse the East Ridge, down-climbing or rappelling the same exposed sections; fixed rappel stations are commonly used on the steepest slabs near the top in place of down-climbing them.