This is an abandoned trail. Only come here if your navigation is up to the task of finding your way where there is no path to follow, and practice Leave No Trace to avoid damaging fragile terrain.

Of all the unofficial, abandoned old trails I've explored at Rainier, this is in by far the best condition. It must have benefited from recent volunteer maintenance. In 2022 I encountered only one significant area of blowdowns, shortly before Evans Creek, which required detouring around.

The trail heads north from Mowich Lake Road, approximately but not religiously following the National Park boundary. It climbs steadily from the start, at first switchbacks, then a long traverse up the east flank of Martin Peak. This offers partial glimpses through trees of Rainier, Echo and Observation Rocks, the North Mowich Glacier, etc. etc. The view is too obstructed to make out details but you can see enough to tell they are there. If a fire or slide were to remove some of the trees, it would be one of the great views of the world. I'm not saying I want anything to harm these trees, but I also don't not want it, if you know what I mean.

The trail then traverses up the west flank of Virginia Peak, descends toward Evans Creek, turns westward, and traverses up the south flank of August Peak, at which point it leaves the National Park and ends at a junction with an old logging road. This feels abrupt (logged forest! areas of bare dirt!) but the sudden openness provides a nice spot to enjoy lunch, sun on your skin, and the only full Rainier view of the trail.

Don't be alarmed if you hear engines near the end of the hike. The network of forest roads outside the National Park is regularly used by dirt bikes and ATVs.

Peakbaggers use this trail to access Martin, Virginia, Berry, and August Peaks, which are nontechnical scrambles to forested summits without views.

Once upon a time the Boundary Trail continued further north, all the way to the Carbon River. The other end of it is still in use as Boundary Trail to Florence Peak. I found what looked like the start of an ongoing route past the end of the current trail, but it was extremely overgrown.