The route description we used for this climb in 1995 came from Mike Garratt and Bob Martin's book. Use either the lower trailhead that starts from the parking area across from the South Mineral Campground, or drive up to the higher trailhead on the Clear Lake road.
From the lower trail head parking lot that can accommodate a large number of vehicles, begin hiking on the well-used and popular trail to Lower Ice Lake Basin. It's less than 2 miles into the lower basin area. The trail levels off some into the basin after a steep section of climbing on switchbacks. If backpacking into here, there are a number of good campsites in the lower basin. Not long after the trail levels in the lower basin, watch for a secondary trail turning off at these coordinates, on the right. N 37° 48' 45.33" W 107° 47' 29.55". This trail leads up first north, then west, then north again across mostly tundra to near Island Lake. Walk on over to the lake.
Hike to the west end of Island Lake on the south side. Head NW up the basin to the saddle between US Grant and V 4. There will be a bench-like area at about 12,700 ft. In earlier season, you may have snow on this part of the ascent so ice axe and/or micro-spikes would be handy. Without snow present, you can gain this bench on mostly tundra. Above the bench, there will be an area of rock rubble to contend with, another smaller patch of tundra and then a loose scramble on talus and rubble to the saddle at 13,220 ft.
from the saddle, we found a clear trail that leads up the south ridge. The trail climbs mostly on small, broken rock between projections of rock outcroppings. it's all easy going through here. Eventually, the trail will lead to a section of ridge that will narrow to just a few feet wide. On both sides, steep, rock-filled gullies drop away. In front of you will be a 12 foot wall, described by G&M. The rock here is quite yellow. A good crack takes you up the wall for 8 feet to a small shelf. The last 4 feet is just a small step up to a 4 foot wide ledge system. We had a short piece of rope with us for this one section, but did not use it. This is the only section that rates at least 3rd class climbing. Some rate this 4th class. The upper ledge we found ourselves on was sufficiently wide and comfortable. It cuts across the south side of the peak at about the 13,600 foot level. Follow it east briefly (about 20 yards) to a wide couloir that's mostly solid rock with smaller rubble laying on top that tends to roll underfoot. The couloir is not too steep. Once out of the couloir, regain the south ridge and follow it to the summit on Class 2+ terrain.
Enjoy the splendid summit view in all directions. If you haven't climbed South Lookout Peak yet, take a hard look at that one. Descend this peak as you came. We would definitely suggest climbing V.4 from the US Grant-V.4 saddle. V.3 to the NW of US Grant is a much more difficult traverse. Derek Wolfe (Furthermore) describes attempting this traverse and says "it did not go." Best features of this hike: Some scrambling on US Grant and the amazing wildflowers of Lower Ice Lake Basin.
Links to other information, routes & trip reports for this peak that may be helpful.