Trail Run Project Logo

Thompson Lake via Mt. Defiance



16.1 mile 25.8 kilometer loop
73% Runnable


Ascent: 5,068' 1,545 m
Descent: -5,067' -1,544 m
High: 5,491' 1,674 m
Low: 2,209' 673 m


Avg Grade: 12% (7°)
Max Grade: 52% (28°)


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

Trail shared by Dean Pospisil

An airy trail with good mountain vistas, and ending at a nice lake pretty far out of the way.

Dean Pospisil

Features Lake · Swimming · Views · Waterfall

Pretty hard to get there when there is still snow on the north ridge past Mt Defiance, should melt by mid-June.


This route takes you through the more crowded Lake Mason, but goes far enough to thin out the crowds. Running along a ridge for much of the way past Mount Defiance you get to see nice mountain vistas and lakes far below you. There is a lot of gain up until Mt. Defiance, and then things are pretty even but continue along a steep ridge, until you're on top of Lake Thompson. From there, you'll enjoy a quick descent to this sizable lake with a few camping spots.


From the trailhead, the path is well-trodden to Mt. Defiance with well-placed signs. It's a lot of steep grades and switchbacks, you'll be surprised how high you get in a hurry. Though you climb quickly, the sound of the I 90 will follow you all the way till Mason Lake, and you may want to just pretend it's a river.

The first stop will be Mason Lake where you can refill your water, stretch out, dip your feet. Continuing past on the marked main trail, you'll see signs where the trail splits to Mt. Defiance and Lake Thompson. Head that way. Again, there is a lot of fairly steep climbing. We were there at the end of May and there was a fair amount of snow to push through. Because of the snow, I would recommend at least having some boots, as kicking into the snow can be helpful for steeper portions.

Once you get to the turn off for Mt. Defiance (if it is a clear day) you'll be able to see Mt. Rainier to the south and maybe even Seattle to the west. You can drop your packs and head up for a better view (20-30 minutes one way), or continue to Lake Thompson. From here you'll cross over to the side of the ridge opposite I-90 and it will get much quieter with fewer people. Runners will first experience some descending before following the ridge for a while until popping up over a final ridge, where a steep switchback descent brings you to Thompson Lake.

In early May, this north facing ridge portion was fully covered in snow and difficult to navigate. To ease your travels, I would recommend poles, good footwear, and the Trail Run Project mobile app which helped us find our way!

Flora & Fauna

We saw the tracks and droppings of a cougar! The lake clearly had some fish in it. A park ranger told us there are a lot more mosquitos when it warms up, but it was cold when we were there, and we escaped the bugs.

Run this trail?

We need help with the following missing trail information:

Need to Know, Runner Notes, History & Background


Rate This Run

Rate Quality

   Clear Rating

Rate Difficulty

Share This Run

Check In


Jul 27, 2018
Bryan E

Trail Ratings

  4.3 from 3 votes


  4.3 from 3 votes
5 Star
4 Star
3 Star
2 Star
1 Star
Run Rankings


in Washington


14 Views Last Month
1,711 Since May 17, 2016



Mount Rainier from the Ira Spring Overlook
Jul 17, 2018 near Riverbend, WA
From the top.
May 11, 2016 near Riverbend, WA
Mason Lake
Jul 1, 2015 near Riverbend, WA
Trail between the overlook and Mason Lake
Jul 17, 2018 near Riverbend, WA
Mason Lake covered in snow
May 8, 2015 near Riverbend, WA
Check out the lower falls on the Ira Spring Trail #1038.
Jun 19, 2017 near Riverbend, WA


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

Shop REI Running