DeadHorse Cave: Washington’s Favorite Lava Tube Cave

I have been wanting to explore Dead Horse Cave, a complex lava tube cave near Trout Lake, Washington, for about three years ever since my friend Zach and I found the lower entrance. At the time we didn’t have a map of the cave, and we knew it was very complex, so we decided not to go in and save our exploration for another time. The next time we were there, about 2 years ago, it was late in the year and the main entrance was nearly flooded with water. Enough to postpone our exploration. Finally, last weekend I got to explore Dead Horse.

Tonya and I drove up the night before and met Evan and Kyron at the pullout next to the logging road that leads to Dead Horse. Because the logging road was pretty rough and required a vehicle with clearance, we left Evan’s Subaru at the pullout and they jumped into the back of the truck. Luckily it was only about .2 miles to our campsite so I didn’t feel too bad for Evan and Kyron bouncing around in the back of my truck.

When we got to the campsite, we set up camp and started a fire. For the rest of the night, we just relaxed and enjoyed the fire while we talked about our caving adventures. I was finally getting my chance to explore Dead Horse Cave.

Dead Horse Cave is No Ordinary Lava Tube Cave

Calling Dead Horse Cave a lava tube cave just does not do it justice. This is no ordinary lava tube cave. Dead Horse Cave is the largest, most complex mapped lava tube cave in the continental U.S. with 14,441 feet of passageways to explore. It’s a complex cave system with several primary tube passages and many more secondary tubes branching off the main tubes. It has large tubes along with smaller tubes with a lot of breakdown to crawl around. There’s also lots of smaller tubes requiring tight squeezes and some places were so small that we had to crawl on our bellies to get through them.

Since none of us had been through the rat hole entrance we decided to start at the lower entrance and work our way uphill to the ledge that leads to the rat hole. We heard running water in the first passage on our left, so we skipped that and worked our way through the lower section until we made it to the river section. I was surprised to see so much water flowing through the underground stream. We followed the stream uphill to the source. The source of the water was two holes in the lava rock. From there we worked our way uphill to the rat hole entrance. After Kyron finished poking around the rat hole, we explored a couple smaller passages off the main passage and then headed back downhill to the lower entrance. It didn’t seem like we were in the cave very long, but we had actually spent about 3 hours exploring the cave. Next time we go back we’ll explore another section. Maybe we’ll even explore the Masochist Maze!

Is it the Longest Lava Tube Cave in the United States?

Dead Horse Cave, at 14,441 feet, is not the longest lava tube cave in the United States, but it is the longest lava tube cave in the continental United States. The longest lava tube cave in the United States is Kazumura Cave on the Big Island of Hawaii. It has been surveyed at more than 40 miles (65 km) long and is also considered the longest and deepest lava tube in the world. Ape Cave, at 12,800 feet, is the third longest lava tube cave in the United States.

What Next?

If you enjoyed exploring Dead Horse Cave, consider exploring Ape Cave near Mount St Helens. Ape Cave offers a striking contrast to tighter, more rugged caves like Dead Horse. Formed by an ancient lava flow from nearby Mount St. Helens, this long, winding lava tube invites visitors to descend into a cool, shadowy corridor where the ground is uneven and the ceiling rises and falls dramatically. As you move deeper, natural skylights and collapsed sections occasionally let in soft beams of daylight, breaking up the darkness and revealing the cave’s rough volcanic textures. The experience feels less like squeezing through a cave and more like walking through a hidden underground passage shaped by fire, making it an accessible but still memorable adventure.

Pairing this underground adventure with a visit to Lava Canyon brings the landscape full circle—here, the same volcanic forces are on full display above ground, where a dramatic gorge, rushing water, and suspended footbridges reveal the raw power that shaped the region.