Three Buttes

Of the three buttes the sign names, only one is open to the public. East Butte and Middle Butte stand on Idaho National Laboratory land, and access is restricted; a road does climb East Butte, to the cluster of radio towers on its 6,572-foot summit, but it is not open to the public. Big Southern Butte, south of here, is public land with a road to the top. For emigrants all three were landmarks across a plain with few others. Today the two eastern buttes stand inside the reactor testing ground the government took over in 1949.

What the plaque says

Three Buttes Rising above this level plain of lava flows and windblown soils, these high landmarks are recent additions to Idaho's landscape. East Butte (farthest east) flowed up and cooled quickly about 600,000 years ago, while Big Southern Butte (south of here) emerged about 300,000 years ago. Although East Butte and Middle Butte have a similar appearance, they were formed in different ways. A dome of melted rock called rhyolite that rose up through a volcanic fissure became East Butte. Middle Butte, however, is a block of hard lava (basalt) pushed up by volcanic activity from below. 428 Text prepared by the Idaho Historical Society Marker made & installed by Idaho Transportation Department

Where it stands

Worth the stop nearby

• Experimental Breeder Reactor I — 15 mi
  The reactor that lit four bulbs in 1951 also suffered the first accidental breeder meltdown, and two engines for a nuclear bomber sit outside.

More markers nearby

• Big Butte — steps away
• Nuclear Reactors — 15 mi
• Lost River — 15 mi
• Elephant Hunters — 18 mi