COVID-19: At REI, we encourage you to get outside responsibly. Stay local, avoid recreational travel, practice social distancing and check ahead for area and facility closures. Learn More
Trail Run Project Logo

Mt. Si



6.6 mile 10.7 kilometer out and back
46% Runnable


Ascent: 3,281' 1,000 m
Descent: -3,282' -1,000 m
High: 3,999' 1,219 m
Low: 717' 219 m


Avg Grade: 19% (11°)
Max Grade: 41% (22°)


Driving directions Take a virtual tour
Zoom in to see details
Map Key

A steep, well-maintained trail takes you atop Mt. Si with outrageous views of Puget Sound.

Benjamin Pontecorvo

Features Birding · Fall Colors · River/Creek · Views · Wildlife

Discovery Pass required year round.


This is a classic, well-traveled run leading to the top of Mt. Si. There is a small portion of scrambling at the summit that is optional.

Need to Know

Go as early as you can. Google Maps may say that the trailhead opens at 6am, but I was there by 5:30am and running with no problems. I met people on the trail who had gone up for sunrise and said they'd started at 2:30am. So no worries about the trailhead not being open.

Expect the trailhead parking to be full by 9am.


From the trailhead, follow the well marked "Mt. Si Trailhead" or just follow the throngs of people on this deservedly popular trail. The endless switchbacks and steep terrain begin almost immediately, and will continue until the very top. This trail offers intermediate terrain that can be useful for both the novice runner and a more experienced outdoors person training for a bigger objective. You'll gain more than 3000 vertical feet in under four miles of beautiful old growth forest. The canopy finally breaks close to the top, revealing some views to the South.

Once out of the forest, there are many outcroppings to enjoy your lunch and some views. Most people will stop here- but the more adventurous can continue uphill and right on a stony path to the Haystack, Mt. Si's true summit. This extra 150 ft of scrambling is class 3/4 and is well worth is as the views to the North are revealed.

On your way down please do not cut trails. What saves you 30 seconds can cause decades of damage. Also you'll need a discovery pass to park at the lot. Have fun!

Flora & Fauna

You will walk over three miles through old growth forest.

Run this trail?

We need help with the following missing trail information:

Runner Notes, History & Background

Is something wrong? Let us know. Have photos to share? Help fellow runners know what's here.

Rate This Run

Rate Quality

   Clear Rating

Rate Difficulty

Share This Run

Check In


Oct 5, 2019
Slambalam Hambone
Jun 16, 2019
David Leech
Go as early as you can. Google Maps may say that the trailhead opens at 6am, but I was there by 5:30am and running with no problems. I met people on t 7.2mi — 2h 01m
May 29, 2019
Auston Sterling
6.6mi — 2h 20m
May 12, 2019
Matt Catallo
Lots of attendants on Sunday morning. Always a great, challenging run. — 2h 00m
Jan 30, 2019
1:17 to top 40min descent
Dec 15, 2018
Christof Dreyer
Dec 7, 2018
Christof Dreyer
Trail clear and dry - one or two muddy spots at the bottom and some icy spots at the top, but no risk of losing traction. 7.2mi
Sep 12, 2018
Vikram Sahney

Trail Ratings

  4.4 from 109 votes


  4.4 from 109 votes
5 Star
4 Star
3 Star
2 Star
1 Star
Run Rankings


in Washington


137 Views Last Month
14,243 Since Jan 23, 2015



Mt. Si Trail
Feb 18, 2015 near Tanner, WA
The "Haystack". People on the left ledge for scale. Look close above the triangle tree on the right, that's a climbing rope- hard core climbers!
May 2, 2017 near Tanner, WA
The Mountain is out! Clear skies abound at the top of Mt. Si.
May 2, 2017 near Tanner, WA
Sunset at the summit.
May 29, 2015 near Tanner, WA
Mount Si.
May 1, 2017 near Tanner, WA
Sun filters through the trees on the only flat part of Mt. Si.
May 2, 2017 near Tanner, WA


Trail Run Project is part of the REI Co-op family,
where a life outdoors is a life well lived.

Shop REI Running