Statistics Roundtrip 8.0 miles
Elevation Gain 3150 ft
Highest Point 3900 ft
User info Dogs allowed on leash Discover Pass required (http://www.wta.org/trail-news/hiking-info/basics/passes-and-permit-info) Getting there
Head east on Interstate 90 and get off on Exit 31 (to North Bend), then drive east on North Bend Way and in less than a mile turn left onto Mount Si Road. Cross the Middle Fork Snoqualmie River bridge at 0.3 miles and drive two miles to the trailhead parking lot (there's room for 200 cars), elevation about 750 feet. Here you'll find the Mount Si Trailhead Park and Picnic Area and a bulletin board with pertinent trail information.
There is also a short wheelchair-accessible loop trail that begins in the parking area. Trail detail The hike begins at the Mount Si Natural Resources Conservation Area parking lot. It climbs from a low-elevation conifer forest to the vestiges of an old burn, now becoming a new forest of firs. The fire dates back to 1910 when Mount Si burned for weeks. At 1,600 feet (about a mile) come to an obvious stopping place, a rocky area with a view to the valley and Interstate 90. Another obvious rest stop is reached at about 1,750 feet, tempting the weary with benches. Snag Flats is reached in another 3/4 mile at about 2,100 feet, the only level section of trail you'll encounter. Just before Snag Flats, a short path descends to a stream, a cool place to rest on a hot day. It is about 2 1/2 more miles to Haystack Basin at about 3,900 feet (four miles total). There are plenty of good rocky perches and benches below the Haystack. Experienced hikers (with a car at the Little Si trailhead) can descend via the Old Si Trail to make a loop. From the base of the Haystack there are views more than 3,000 feet straight down to the valley and I-90, as well as out to the Olympic Mountainsand Seattle.