Mount Si is a well known landmark and a very popular hiking destination, located in the Cascade foothills just east of Seattle. The mountain looms over the town of North Bend, its steep west face rising thousands of feet to craggy pinnacles. As the first high, jagged summit a traveler sees while heading east on I-90, it is an integral part of the rampart that the Cascade Range presents to the Puget Sound area.
A well-graded trail climbs about 3300 vertical feet (from 600 to 3900 feet) in 4 miles to just below the summit "haystack". This is an extremely popular and crowded trail, with estimates of 80,000 - 100,000 users per year, an average of 250 per day (obviously higher than that on sunny summer weekends). Fortunately, a 1993 reconstruction of the trail by the state allows it to handle the load quite well. The ascent is continuously steep and almost entirely in deep forest, with few views between the trees. But near the top, just below the haystack, rocky crags provide spectacular vistas westward over North Bend and the Snoqualmie Valley to Seattle skyscrapers, Puget Sound, and the Olympic Mountains.
Many hikers scramble up the haystack to the very summit, an exposed, hands-needed semi-climb that is not for the acrophobic. The thousands that regularly ply this route have already dislodged all the rotten or loose rock long ago, leaving a nice staircase with good handholds. Still, people have been killed in falls on this short pitch, so be very cautious and don't try it in any kind of bad weather. The view is not too much better at the end of this 200-foot scramble.
In strict topographic terms, Mount Si is not very prominent at all, despite its very impressive west face. To the east, a high, wooded saddle connects Mount Si to an unnamed 4560 peak that is almost 400 feet higher than its famous satellite summit, and beyond that the ridge runs to higher peaks like Mount Teneriffe, Green Mountain, and other forested bumps of little renown.
Note that the USGS topographic map is misleading as to the location of the summit. The spot elevation of 4167 is the lower north summit, and the Haystack (the southern and highest summit) has no marker or elevation on the map. Based on King County GIS contour data, the elevation of the Haystack is over 4180 feet.
Mount Si was named for Josiah "Uncle Si" Merritt, an early local settler. It is pronounced "Mount Sigh", just like the middle syllable of "Josiah".