Ape Cave

Useful Information

Location: Gifford Pinchot National Forest, south of Mount St. Helens.
I-5 exit 21 (Woodland Exit), WA-503 East, then FR-90, through Cougar. Turn left (north) onto FR-83 for 3.5km, turn left (west) onto FR-8303, 2km to the Ape Cave parking area. 100m walk from the parking area to the cave.
Open: No restrictions.
Fee: free.
Classification: ExplainLava Tube
Light: None, bring torch. Lantern rentals at Apes headquarters on the south side.
Dimension: L=3,983m, VR=182m, T=5°C.
Guided tours: Self guided. Lower cave: L=1,200m, D=1h. Upper cave: L=2,000m, D=2.5h
Address: Gifford Pinchot National Forest, Forest Headquarters, 10600 N.E. 51st Circle, Vancouver, WA 98682, Tel: +1-360-891-5000, Fax: +1-360-891-5003.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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1951 a bulldozer operator clearing brush nearly dropped into the entrance.
1951 first explored by the St. Helen Apes.


Ape Cave is a lava tube, located south of the infamous Mount St. Helens in Gifford Pinchot National Forest. It was formed by a lava flow from Mount St. Helens about 1,900 years ago. It is of rather impressive size, and was the longest lava tube in the continental United States some times ago. Today (2005) it is second after nearby Deadhorse Cave. Of course, there are numerous longer lava tubes on Hawai'i.

The cave is not developed like a show cave, but there are two cave tours and a surface trail with interpretive signs. Bring warm clothing, sturdy boots, a helmet, and at least two sources of light. Good light is essential, as the lava is rather dark. At Apes headquarters on the south side lanterns may be rented and a map is also available.

The trail through the lower cave takes about one hour. This part of the cave is fairly level and the floor is covered by mudflow, which makes it rather easy to walk on. Highlight is the Lava Ball, a strange formation of lava in the ceiling. The upper cave is for the more adventurous as it is necessary to climb over large rock piles. The most difficult spot is a 2.40m high lava fall which must be climbed. The cave visit is completed by an interpretitive trail above ground, called Ape Cave Trail. It brings cave visitors through the forest and across some recent mudflows back to the main entrance. Of course it is possible for the less sportive, to skip the cave and just hike the trail.

The cave was discovered in 1951 by a bulldozer operator, who was clearing brush. He nearly fell into the hole which was 4.5m in diameter and 7m deep. Soon it was explored by the St. Helen Apes, a local group of outdoorsmen, who dubbed it Ape Cave.