The Ape Cave – Cougar, Washington - Atlas Obscura

The Ape Cave

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous. 


Located on the south side of Mt. St. Helens, the Ape Cave was formed over 2000 years ago when lava flowed down the volcanic mountain in streams.  As the lava cooled an outer crust would form, allowing the molten lava inside to continue to flow and creating tunnels. This kind of formation is unusual for the Cascade Range volcanoes, which seldom erupt with fluid lavas.

Named after its original explorers and not the hairy, ape-like humanoids said to roam the surrounding mountainside, two and a half miles of lava tube remains today, luring cavers to explore its narrow passages and crawlways.  Lined with stalactites and stalagmites, the cave is scattered with boulder piles and for the more adventurous climbers an 8-foot lava fall can be scaled to reach a cathedral-like skylight opening.  

Tales of purported sightings of Sasquatch (aka “Bigfoot”) have come from the area for decades, but the tube actually received its name from the Mt. St. Helens Apes, the group of foresters who first explored the cave soon after its discovery in the early 1950’s. No evidence of habitation by the legendary giant hominids is known to have been found in the caves.

Keep your camera ready, regardless.

Know Before You Go

Reservation required. Cave open to the public May-October. 

From Cougar, drive east on Forest Road 90 just 1 mile beyond the Swift Dam, and turn left (north) onto FR 83. Drive 2 miles on FR 83 and turn left onto FR 8303. Continue for 1 mile on FR 8303 to the trailhead on the right.


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