Ptarmigan Trail to Cosley Lake [CLOSED]

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Glacier National Park

Ptarmigan Trail to Cosley Lake is a 42.8 kilometer moderately trafficked out and back trail located near Babb, Montana that features a lake and is only recommended for very experienced adventurers. The trail is primarily used for hiking, nature trips, and bird watching and is best used from March until September.

Distance: 42.8 km Elevation Gain: 1,760 m Route Type: Out & Back


nature trips

bird watching




wild flowers



no dogs

This trail is experiencing full or partial closure due to COVID-19. Please see the open trails nearby for alternate hiking options.

10 months ago

From the parking lot to the tunnel (and walking through it and looking at the other side/taking pics) and back was approximately 11.25 miles. Significant gain at the end portion of the hike past Ptarmigan Lake. Very exposed so wear sunscreen. Be aware of falling rocks on the other side of the tunnel. Today was super windy and a rock fell down from the cliff above and hit me in the head really hard. Luckily wasn’t bleeding, but felt dizzy for a while and have a huge bump. If you or a loved one are afraid of heights I would not recommend. The part past the lake to the tunnel is on a super thin path climbing up the edge of a cliff for a substantial amount of time. Beautiful scenery all together.

Mon Jul 30 2018

Loved this hike! Long, challenging, plenty of wildlife. Be loud if you're alone-hikers in front and behind me saw a grizzly w 2 large cubs! The lake is gorgeous, crystal clear and super refreshing on the feet. Nice place for lunch before heading back, or continuing up to the tunnel. From the lake up, it's long switchbacks. The reward is a cool walk through to an amazing view of Helen lake and rock walls. Watch your belongings, the chipmunks and marmots will steal them!

Mon May 14 2018

This was a great section of trail and a highlight from my 2017 backpacking trip in Glacier.

Wed Jan 04 2017

Challenging and beautiful. There is a portion of the trail that is a fairly steep climb. Well worth the effort to get to the tunnel and lake. Beautiful views!

Mon Aug 15 2016

Started at the Swiftcurrent Motor Inn hiked past the Ptarmigan Falls, and Ptarmigan Lake. Very beautiful trail, lots of cool people. This is a pretty difficult trail, you ascend 2,300ft. I definitely recommend this trail!

Thu Mar 17 2016

It is a scenic hike. Once you take the cutoff to go to the tunnel, there is a pretty steep climb then it levels off. We hiked it in July and were not prepared for the weather. It was cold when we started in the morning and when we reached the tunnel, it was completely covered by a cloud. On the way down, it rained, thundered and hailed on us. So go prepared for all weather. It can change in a heartbeat.

Wed Nov 11 2015


Sat Aug 29 2015

Great hike, saw a grizzly up close. Elevation gain is quite gradual except the final switchbacks. Not too hard at all with great views!

Mon Aug 04 2014

Second best hike I took in Glacier only to the Highline Trail. This one is tough, with three separate tough elevation gains throughout the trail to the tunnel. The last march up the switchbacks was tough but the view kept getting better, which always alleviates the pain for me. Definitely watch out for bears on this one, especially early in the morning. I had three near misses cause I left before 8 AM. Wait a little longer, it may be hot for you but it's also hot for them and they go sleepytime :) Great great great hike loved it!

Sun Sep 29 2013

Wowza! Strenuous with little moderation. Wooo hooo! Switchback heaven OR hell depending on your perspective. Unimaginable beauty, and a defining point would be the totally different vista when you exit the tunnel on the other side. This hike rates right up there as one of my favs because you have an immediate kick your butt elevation gain and then you have an immediate kick your butt elevation gain and THEN you have Lake Ptarmigan for a nice 'soak your feet in a cold pristine alpine lake and rinse your head wrap.' After that? Yah, the switch back with a major kick your butt elevation gain, for a total of 2500 feet. Do it!

Mon Aug 26 2013

Fantastic trail- breaks off into a Y from the Iceberg Lake Trail. It's amazing to think about how the tunnel and the trail leading up to it was built, and all the history behind it. Steep at times, but worth it to see beyond the tunnel- the views beyond are absolutely phenomenal. I felt like I had crossed into an alternate space-time continuum going from Glacier National Park into some Tolkien-esque realm of fantasy. Definitely hike down past the other end of the tunnel, truly a magical sight to see.

Mon Jan 28 2013

Stunning hike, it was our favorite hike on our backcountry trip through the north-eastern portion of Glacier. If you're day-hiking this, I highly suggest trekking the extra couple miles BEYOND the tunnel! You won't regret it!

Tue Apr 03 2012

Loved this hike! combined with iceberg lake for a nice, somewhat long day hike. Wonderful example of good GNP hiking

Sat Mar 24 2012

What an amazing hike! There was a Youth Group hiking at the time we were so that made for a few more people than what is the norm. Great views, what a feeling of accomplishment since it really kicked my butt!

Sun Apr 18 2010

Wonderful Hike! Glacier National Park is Amazing!

9 months ago

9 months ago

10 months ago

Fri Jul 20 2018

Sat Nov 11 2017

Thu Jan 14 2016

Mon Jul 27 2015

Wed Jun 10 2015

Thu Jan 01 2015