Adventure Pass required for parking. Trail enters San Gabriel Wilderness at 1.1 miles. There are two official Mt. Waterman Trails. This trail (10W05) is formally named "Mt. Waterman Trail #2". The trail from 3 Points (10W04) is "Mt. Waterman Trail #1".
The Mt. Waterman trailhead is across Hwy 2 from the Buckhorn Day Use Area. Use the large turnouts along Angeles Crest Highway and not the limited parking in the day use area.
Follow the trail to the left as it carries you just above the highway, across a dirt road, and then up through the manzanita, away from the road. The trail continues south, along the flank of the mountain, through a forest of pine and cedar. It then opens up to a northwest facing ledge before carrying you to the main ridge at about 1 1/4 miles in.
From here, the view opens up to the south and you can look out over the San Gabriel Wilderness. The trail follows the ridgeline west, up the shoulder of the mountain for 1/2 mile, before traversing a set of long switchbacks. At 2 miles there is a signed junction with the Mt. Waterman Trail #10W04
that goes to 3 Points.
Take the trail to the right (north) and follow it as it turns west, around the backside of a shoulder peak and then continues on to the main peak.
Just shy of the 3 1/2 mile mark there will be a small mileage sign. From here, the trail heads southeast, toward the rocky summit. To reach the 8038' official height of the mountain, you'll need to climb some rocks!
Jeffrey, sugar pines, white fir, incense cedar shade much of the trail. Deer and occasionally bighorn sheep can be seen.