Idaho's Mammoth Cave

Useful Information

Location: 13 km north of Shoshone, ID. Leave Interstate 26 or 93 at Shoshone, follow Hwy 75 nort for 13 km, turn lefts. Well signposted.
Open: Summer daily 9-18.
Fee: Adults USD 8, Children (7-16) USD 4, Children (0-6) free.
Ticket includes both museum and cave.
Classification: SpeleologyKarst cave
Light: propane lanterns provided, bring torch
Dimension: T=5 °C.
Guided tours: self guided, L=800 m, D=30 min.
Address: Idaho's Mammoth Cave
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1902 discovered by early settlers.
1954 discovered and explored by Richard Olsen and his girl friend Veneda.


Idaho's Mammoth Cave also includes the Shoshone Bird Museum of Natural History which is located in timber huts above the cave. The museum is a weird collection of taxidermy and many other strange things. Most of the animals are birds, but there are also wolves, snakes and insects. There a sheep with two heads or with two bodies and the skeleton of a bear.

This place is located in a desert of volcanic rocks, mostly basalts, and the cave below ground is a lava tube. Actually it has nothing to do with Mammoth Cave in Kentucky, so do not mix them.

The cave was known at least since 1902, but when Richard Olsen stumbled across the cave entrance while hunting bobcats in the area, he was fascinated. Legend tells he walked back to the car 12.5 miles to fetch a torch. When the two entered the cave his girlfriend started to cry because she got scared and she cried all the way in and out. Soon after Richard Olsen got title to the cave under the Small Tract Act. During the first years he used the cave to grow mushrooms.

The lava tube has a sign at the door with a radiation warning symbol and the words Fallout Shelter. We guess the cave was dedicated a civil defense shelter during the Cold War, obviously a very bad idea, as percolating ground water would transport radioactive fallout into the cave pretty fast. However, the government graveled a good road to the cave and stored food and supplies on a platform in the cave for about 20 years. The reason was nearby Mountain Home Air Base which was home to a fleet of B52s which carried the H bomb. Obviously the base was a preferred target of the Russians.

After the road was built Richard and his wife Linda opened the cave to the public.

The cave is visited on self guided tours and visitors are informed by signs. They tell about the "sort of" cave bears which hibernated inside the cave. Actually there were never cave bears (Ursus spelaeus), as this now extinct bears lived only in Europe. Early visitors left their names and the year on the wall, the earliest date from 1902. At the end of the tube, the ceiling is 15 m high and the cave is covered by a 15m thick basaltic lava flow. At this point the sign tells: "THE TRIAL ENDS. DONOT GO ANY FARTHER ... (NO DIGGING IN CAVE PLEASE)". A good advice we guess.