Mount Si

The trail begins in mixed second-growth forest along the old Mount Si road grade, climbing steadily through Douglas fir and western red cedar. At roughly 1.5 miles, the forest transitions into Snag Flat, a surviving stand of old-growth timber that escaped both fire and logging. The massive trunks here, some over 500 years old, mark the beginning of the trail's steeper pitches.

Above Snag Flat, the grade intensifies through a series of switchbacks gaining roughly 2,000 feet in the next two miles. The forest thins as elevation increases, and rocky openings provide the first views south toward Mount Rainier and across the Snoqualmie Valley. Mountain goats inhabit the upper rocky slopes and are regularly spotted near the summit clearing.

The main trail ends at a broad rocky viewpoint at 3,900 feet with panoramic views spanning Mount Rainier, the Olympics, and the Seattle skyline. Beyond the viewpoint, a rough scramble leads up the Haystack, a craggy false summit roughly 100 feet higher. The Haystack requires Class 3 moves on loose rock and is not recommended for inexperienced scramblers. The exposure is real, and the rock quality is poor.

Mount Si draws over 100,000 hikers annually, making it the most heavily trafficked trail in Washington state. Expect company at all hours, particularly on weekends from May through October. The parking lot fills by mid-morning on sunny weekends, and Discover Pass enforcement is regular.