Mt. Si

Climb to the spectacular Mt. SI summit via the Old Trail

Hike Length: 14 miles

Elevation Gain: 3500 feet

Hike Difficulty: Strenuous

Map: Green Trails ”Mt. Si” #206S

Revised 9/20/2021

Mt Si’s imposing wall of rock, rising several thousand feet above North Bend, is a product of powerful geologic forces working over countless millennia. The rock that Mt Si is composed of actually originated underneath the floor of the Pacific Ocean. For many millions of years a large chunk of the earth’s crust underlying the Pacific has been slowly colliding with the land mass of the Northwest in a process that geologists call “subduction” . This continuing collision generated the forces that heaved up the Cascade Mountains, along with the chunk of ocean floor that Mt Si is made of. A fault --a zone of weakness in the earth’s crust--at the the western face of Mt Si helped create the straight, extra-steep mountain wall that begins at Mt Si and continues many miles north.

More recent geological mayhem occurred in the form of the most recent Ice Age, a “mere” 15000 years ago. During that time, a massive ice sheet filled the Puget Sound basin to a depth of thousands of feet, steepening Mt Si’s cliffs even more as the flowing ice sheared off rock off the mountain’s base. For the finishing touch, the ice sheet also dammed all of the west-flowing Cascade Mountain rivers, creating at times a huge “ice marginal river” that flowed south along the western base of the Cascades. This Columbia River -sized torrent acted as a powerful force of erosion., creating among other things the deep cleft between LIttle Mt Si and Big Mt Si.

This part of North America remains geologically active to this day, as the Cascade volcanos such as Mt St Helens, as well as the frequent earthquakes in the Seattle area, attest to in dramatic fashion. Something to think about as you hike up the trail to Mt Si on a calm, sunny day on the seemingly “terra firma”.

Most hikers these days use the “new trail” that starts several miles from North Bend on Mt Si Road. The old route to Mt. Si was abandoned for many years after logging destroyed parts of the trail and private property blocked access at the lower end. But the old trail has enjoyed a bit of a renaissance in recent years. Hikers tired of the crowds on the new trail, or just looking for a change of scenery, have worked out new access routes to the old trail, and even provided it with a little maintenance. In general the old trail is quite rough and steep, although long stretches of the trail are in surprisingly good condition. The good news for bus hikers is that the old Mt. Si trail is much more bus-friendly than the new version, requiring much less road slogging to get to the trailhead. The Little Si trailhead (see Little Si page) provides access to the old Mt Si trail.

Mt. SI is a long, strenuous hike to sub-alpine country. Get in shape before tackling this hike, and carry warm clothes, as it can be cold and windy on top. The upper elevations of Mt. Si are usually covered with snow and ice in winter, sometime as late as April. Using trekking poles and traction aids such as instep crampons, "Yak Trax", or similar devices can be helpful when the trail is icy.

The summit "Haystack" of Mt. Si

Getting There

Ride Sound Transit 554 to Issaquah Transit Center. Transfer to Metro 208 (thin schedule, no Sunday service - plan transfers carefully) and ride to downtown North Bend at Bendigo Boulevard and W 2nd Street).

At the Mount Si Senior Center, you may consider transferring to Snoqualmie Valley Transit's dial-a-ride bus, which can take you directly to either the little Mt. Si or new Mt. Si trailheads. Advance arrangement is required and there is no service on weekends.

The Hike

Walk to the Little Si Trailhead as described in the chapter covering Little Si [1.8 miles, 500’]. Follow the Little Si trail as it quickly climbs up rocky ledges of an old quarry, then levels out on a forested bench.

Turn right (east) onto the Boulder Garden side trail, which descends slightly to join up with an old road bed which has decayed into a very nice footpath. The road climbs the thickly forested hillside in broad switchbacks, passing several impressively tall, mossy cliffs along the way. After a brisk climb, the trail levels out on a saddle on a ridge top.

To get to Mt. Si, take the left (uphill) trail that leaves the old road bed. This delightful stretch of trail, part of the Boulder Garden Loop, climbs at an easy pace through thick douglas fir/hemlock forest, passing many mossy ledges and boulders. In a short half mile, it reaches a junction with the Old SI trail, whose tread is much steeper and rougher [3.2 miles, 1350’]. Go right (uphill); the left branch goes back down to the Little Si trail and can be used as an alternative route to get to this point.

The old trail climbs briskly through the woods on rocky, rough tread. The path levels off briefly when it approaches the base of a cliff, then gets very steep and poor as it scrambles up alongside the cliff’s edge. Once on top, there,s a bit of a view [3.8 miles, 1750’]. The trail continues on a steep and rough course until it reaches the bed of an old, overgrown logging road, where there’s a short respite from the climbing [4.0 miles, 1900’]. The trail follows the logging road for a bit, then turns back into pure trail, making long switchbacks up a steep, viewless slope. The trail here, though steeply graded, is in surprisingly good condition, perhaps protected from erosion by the dryness of this south-facing slope. The dry soil conditions encourage an almost pure growth of oregon grape and sallal under the “hem/fir” forest canopy.

The trail eventually reaches an indistinct ridge and climbs it in short switchbacks [5.5 miles, 3000]. Tantalizing, limited views open up out over the North Bend valley, which looks really far down from here. Not long after this point, the trail gains the crest of a much broader ridge, and an unsigned junction with the new Mount Si trail [5.9 miles, 3300’].

Remember this spot carefully, because you don’t want to miss it on the way down. It’s not a huge disaster if you do miss the junction and end up at the New Si Trailhead, but you are faced with a 2+ mile road slog on Mount Si Road to get back to the Little Si trailhead.

Go left and follow the New Si trail uphill. In comparison with the old trail, this trail is wider and more gently graded. It’s pleasant walking, but you may be shocked at the number of other hikers on the trail, even on weekdays. Just past an elevation sign indicating 3620’, the trail passes a breathtaking viewpoint looking SE toward the Cascades. Then the trail makes a switchback and climbs to an alpine-feeling ridge top, where the terrain becomes open and rocky, and the trees small and wind-battered. Clumps of beargrass grow among the boulders. Finally the trail seems to come to an end at the base of a rocky crag [6.7 miles, 3900’], where impressive views open up in every direction. The snowcapped cone of Mt. Rainier can be seen to the south.

Actually the trail continues on from here, climbing over the crag on cement and rock steps. Shortly beyond, the trail enters the Mt. Si basin [6.8 miles, 4000’], beyond which the summit “Haystack” of Mt. SI looms, a great cliff of dark- colored rock (technically, its meta-gabbro, for you geology buffs). Around the meadowy floor of the basin grows an interesting mix of trees, including clumps of silver fir and even a few lodgepole(shore) pines, indicators of the harsher climate at this elevation.

At the edge of the basin there is a signed junction, where trails branch off to a viewpoint and the Haystack climbing route. The viewpoint is truly impressive, perched at the edge of a steep slope dropping 3500’ down to the North Bend valley. Benches are provided so that you can take in the awesome view in comfort. For most people, this spot makes for a most worthy destination and endpoint for the Mt. SI hike.

Getting to the top of the Haystack is a tricky, somewhat dangerous scramble. Nevertheless , many people do it. A trail also can be found that heading toward Mt. Teneriffe, although that is way beyond the scope of what most bus hikers will want to do

Getting Back

The Metro 208 bus to Issaquah Park&Ride leaves roughly every two hours from Bendigo Avenue in downtown North Bend. If the bus is not coming for awhile, the KIng County Library on 4th and Main is a good place to spend some time. Ride the bus to the end of the line at Issaquah Park&Ride, where connections are good to downtown Seattle via the Sound Transit 554 bus.