Bring water, as there isn't any along the trail, and no amenities whatsoever at the trailhead. After parking, a look around Towhead Gap will reveal two battered trailhead signs, on opposite sides of the road. You want the one on the northwest side, where the road first widens to form the parking area. The sign may still be legible: “High Rock Lookout Trail 266.” Immediately to the right is what looks like a wider trail heading up. Ignore it; it narrows into an eroding boot path that connects with the main trail in a tenth of a mile.
The main trail starts out somewhat narrow, and lined with vegetation. After connecting with the boot path, it follows the ridgeline up, entering a forest of young fir and hemlock that provides shade for most of the climb. The trail is adequately wide the rest of the way. Huckleberries are plentiful along the lower part. Bear grass, trilliums, and penstemon are less common.
The ascent is moderately steep and has few switchbacks, climbing steadily to the north-northwest just below or along the crest of Sawtooth Ridge. The tread is good, with few roots or rocks to contend with. At 0.7 and 0.9 miles are wooden benches, offering a convenient place to rest. From here on, the trail steepens, as trailside vegetation thins in favor of larger trees.
At 1.3 miles, the trail tops the ridgeline at a rock outcropping and viewpoint. A steep drop-off prevents getting an easy view of the summit, but it is close. Continue up the west side of the ridge top, passing below the visible lookout, to the northern edge of Sawtooth Ridge, where the sheerness of the northern face becomes apparent. Turn right for the final 200 yards, onto the large and flat sloped rock that the lookout building is fastened to. The lookout was built in 1929, but is no longer staffed. Building occupancy is prohibited due to the lack of lightning protection.
The United States Geological Survey classifies High Rock as a “pillar,” a “vertical, standing, often spire-shaped, natural rock formation.” The exposure on this pillar is worthy of caution; there are no longer any cables to protect you from a sheer vertical drop, as much as 600 feet on the north side. Enjoy the views from the rock or from the wraparound deck of the lookout. Mount Rainier is to the northeast, as is Cora Lake, over 1,800 feet below you. Admire the rocky cliffs to the west, or just gape at the treetops so far below.