Craters of the Moon National Monument in Idaho is a dramatic volcanic landscape of ancient lava fields cinder cones and lava tube caves that offers hikers stargazers and curious adventurers an unforgettable and truly otherworldly experience in the American West.
Idaho: Arco and Experimental Breeder Reactor #1 (EBR-1)
☢️ Idaho’s Nuclear Secret: More Explosive Than You’d Expect
The eastern reaches of Idaho, north of Idaho Falls, are about as bleak and remote as it’s possible to be without actually being on the moon. Miles of high desert scrubland, sagebrush, not much else. Which, if you think about it, makes it absolutely perfect for storing dangerous things. Nobody’s going to complain. There aren’t enough people nearby to complain.
It was precisely this splendid isolation that caught the eye of the Federal Government back in 1942, when the area was first commandeered for testing naval artillery during the Second World War. Enormous guns, fired into the desert. You can imagine the neighbours weren’t thrilled — if there had been any neighbours. Then, in 1949, with the Cold War beginning to properly get its teeth into everyone’s nerves, the government went looking for somewhere suitable to build its first nuclear reactors. Somewhere quiet. Somewhere nobody would ask too many awkward questions. They came back to Idaho.
The result was what is now known as the Idaho National Laboratory — a 890-square-mile tract of federally-owned land administered by the U.S. Department of Energy. In Idaho Falls, locals don’t bother with the full name. They just call it “The Site,” which, frankly, sounds more like a gangster film than a centre of scientific achievement, but there you are.
🔬 Seventy Years of Things Going on That You Knew Nothing About
And here’s the thing — I genuinely had no idea. None. Zero. I’d never given a moment’s thought to Idaho’s role in the history of nuclear power, which is a bit embarrassing when you discover quite how significant it’s been. Over the past seven decades, some of the most consequential advances in nuclear energy have happened right here, in this forgotten corner of a state most people only associate with potatoes. The laboratory remains, to this day, the United States’ leading nuclear energy research facility, though its work has broadened considerably to include alternative energy sources and, rather more soberly, cybersecurity. The world moves on, even in the desert.
It has also, it must be said, seen its share of tragedy. In 1961, a reactor accident at the site — SL-1, if you want to look it up — killed three workers and remains, to this day, the only fatal nuclear accident in American history. It’s not the sort of thing the tourist brochures lead with, but it happened, and it’s part of the story.
💡 EBR-I: Where Four Light Bulbs Changed Everything
⚡ Experimental Breeder Reactor I
Tucked away on The Site is one of the genuinely remarkable places in the history of modern civilisation, which is quite a claim for a squat, rather unglamorous building in the Idaho desert. The Experimental Breeder Reactor I — EBR-I to anyone who works there, or ERB-I if you’re me and you’ve misread the sign — is a decommissioned research reactor, a U.S. National Historic Landmark, and, rather wonderfully, the world’s first breeder reactor.
On the 20th of December 1951, the reactor was switched on for the first time. What happened next was, by any measure, historic: it generated enough electricity to illuminate four 200-watt light bulbs. Four. Now, I’m aware that doesn’t sound terribly impressive — my bathroom has more wattage than that — but this was the first time in human history that a nuclear reactor had produced usable electrical power, and those four bulbs represented something enormous. Shortly afterwards, EBR-I was generating enough electricity to power the entire building it sat in, and it continued operating as an experimental facility until it was formally decommissioned in 1964, having contributed enormously to the scientific understanding of how breeder reactors work.
Today, EBR-I has been converted into a museum, open to visitors from late May through to early September each year — free of charge, which is more than can be said for most things in America. Sadly, when we passed through the area, it was closed due to COVID-19 restrictions, which meant we had to content ourselves with a view of the building from the road. A historic landmark, glimpsed through a windscreen. Brilliant. Still, at least we knew it was there, which is more than we did before we set off.
🏙️ Arco: The Little Town That Split the Atom (Well, Sort Of)
There are towns that make history, and then there are towns that make history completely by accident whilst containing barely enough people to fill a decent-sized pub. Arco, Idaho, falls firmly into the second category. With a population of around a thousand souls — and I’m being generous — it sits in the high desert south of the Idaho National Laboratory looking, to the casual observer, like absolutely nothing is going on. And yet, on the 17th of July 1955, Arco became the first town in the entire world to be powered entirely by nuclear energy. Not bad for a place that, not so long before, had been called Root Hog.
Yes, Root Hog. Nobody seems entirely sure why. These things happen in the American West and it’s generally best not to ask too many questions. The town was eventually renamed Arco, after a German scientist by the name of Georg Von Arco, who made his name in radio transmission technology in the early twentieth century. How a German radio pioneer ended up lending his name to a small Idaho desert town is the sort of question that historians presumably wrestle with at three in the morning, but there it is.
⚡ One Hour That Changed Everything — Then Back to Normal
The great nuclear moment came courtesy of the Borax-III experimental reactor, operating at what is now the Idaho National Laboratory site. On that July afternoon in 1955, the reactor was powered up and the conventional electricity supply, provided up to that point by the Utah Power and Light Company, was gradually withdrawn and replaced with nuclear-generated power. The whole of Arco — every light, every refrigerator, every single thing drawing current — was running on the power of the atom.
It lasted about an hour. Then they switched it back to Utah Power and Light.
Which is, I think you’ll agree, either a magnificent footnote in the history of human progress or a very expensive way of proving a point, depending on your outlook. But the point was proved, the record was set, and Arco has been dining out on it ever since — quite rightly, as it happens. The town’s rather charming little city hall wears its achievement proudly, with a sign on the outside that announces Arco’s place in history to anyone who passes. In a town of a thousand people in the middle of the desert, you take your bragging rights where you can find them.
🚢 A Submarine Conning Tower. In the Desert. Obviously.
On the road into Arco from the direction of the National Laboratory, there is a small pocket park that rewards a brief stop. It contains a handful of exhibits, most of which are perfectly expected given the area’s nuclear heritage. And then there’s the conning tower of the USS Hawkbill, a decommissioned nuclear-powered submarine, sitting in the Idaho desert approximately as far from the ocean as it is physically possible to be in the continental United States.
The Hawkbill was a Tullibee-class vessel — actually, she was a Sturgeon-class fast-attack submarine, commissioned in 1971 and decommissioned in 2000, with a career that included operating beneath the Arctic ice pack. Her conning tower — technically called a sail, though as the information board notes with admirable honesty, a sail is not a particularly useful method of propelling a submarine — now sits in a car park in landlocked Idaho, which feels like either a fitting tribute or a very long way from home, depending on your sympathies.
What makes the Hawkbill particularly memorable is her hull number: 666. This earned her the nickname the “Devil Boat,” a label which is entirely coincidental and has nothing whatsoever to do with occult worship. Almost certainly. Probably. The park also features a torpedo on display alongside the conning tower, which completes the slightly surreal tableau rather nicely. It is, needless to say, an absolutely brilliant photo opportunity, and if you drive past without stopping, you’ve only yourself to blame.
Planning Your Trip to Arco
🚗 Getting to Arco, Idaho
Arco is a small, remote town in central Idaho with no public transport links. A hire car is essential.
| ✈️ Nearest Airport | Idaho Falls Regional Airport (IDA) — 68 miles / approx. 1 hr 15 min drive | 🛣️ Main Route | Junction of US Highway 20/26 and Highway 93 in Butte County |
| ✈️ Alternative Airports | Pocatello Regional (PIH) — 86 miles; Boise Airport (BOI) — 187 miles | 🏙️ From Idaho Falls | ~70 miles west on US-20/26, approx. 1 hr 15 min |
| 🏙️ From Boise | ~200 miles east on I-84 then US-20, approx. 3 hrs | 🏙️ From Salt Lake City | ~245 miles north, approx. 3 hrs 45 min |
🌋 Craters of the Moon National Monument & Preserve
| 📍 Location | 1266 Craters Loop Road, Arco, ID 83213 — 18 miles west of Arco on US-20/26/93 | 🕖 Opening Times | Daily, 8:00 AM – 4:30 PM (extended summer hours; closed some winter holidays) |
| 🌐 Website | nps.gov/crmo | 📞 Phone | 208-527-1300 |
| 🚗 Getting There | Drive west from Arco on US Highway 20/26/93 for 18 miles; paved access road to visitor centre | 🏕️ Camping | Lava Flow Campground — $15/night, first-come first-served |
🎟️ Entry Fees
| Per Vehicle | Per Motorcycle | Per Person (foot/bike) | Under 16s |
|---|---|---|---|
| $15 | $10 | $7 | Free |
ℹ️ Fees cover 7 consecutive days. Free cave permit required for lava tube caves — obtain at visitor centre. Free wilderness permit required for backcountry overnight stays. America the Beautiful annual passes accepted.
⚛️ EBR-I Atomic Museum (Experimental Breeder Reactor-I)
| 📍 Location | US Highway 20/26, Idaho National Laboratory Site — 18 miles east of Arco, 50 miles west of Idaho Falls | 🕖 Opening Times | Memorial Day to Labor Day, daily 9:00 AM – 5:00 PM (summer season only) |
| 🌐 Website | inl.gov/ebr | 📞 Phone | 208-526-0050 |
| 🚗 Getting There | Drive east from Arco on US Highway 20/26 for 18 miles; well signposted from the highway | 🗺️ Tours | Self-guided and guided tours available; no reservation required |
🎟️ Entry Fees
| Admission | Groups |
|---|---|
| Free | Year-round group tours by arrangement |
ℹ️ Open summer season only (Memorial Day to Labor Day). National Parks Passport stamps available on site. No reservations necessary for individual visits.
Opening times and seasonal dates may vary year to year. Visitors are advised to confirm current details before travelling, particularly for EBR-I which operates on a seasonal schedule.
The Best Time to Visit Idaho
🌸 Spring in Idaho (March–May)
Spring transforms Idaho gradually, with lower elevations thawing out by March whilst mountain passes remain snow-covered well into May. This is one of the most rewarding times to visit for nature enthusiasts. The Bitterroot and Clearwater valleys burst into wildflower bloom, and rivers run fast with snowmelt — making it prime season for whitewater rafting on the Salmon and Payette rivers. Birders flock to the Snake River Birds of Prey National Conservation Area, home to one of the densest concentrations of nesting raptors in North America. Temperatures are pleasant but variable, ranging from around 5°C in the mornings to 18°C on sunny afternoons. Crowds are thin, prices are lower, and the landscape feels wonderfully fresh.
What to pack: Lightweight moisture-wicking base layers, a waterproof and windproof jacket, fleece mid-layer, sturdy waterproof hiking boots, sunscreen, sunglasses, and a compact day pack. A warm hat and gloves are wise for early mornings and higher elevations.
☀️ Summer in Idaho (June–August)
Summer is Idaho’s high season and for good reason. The weather is reliably warm, trails are fully open, and the state’s remarkable outdoors — from the Sawtooth Mountains to Craters of the Moon — is at its most accessible. Temperatures in the lower valleys can climb to 35°C, whilst mountain areas stay pleasantly cool. This is the best time for multi-day backpacking, fishing in pristine alpine lakes, and attending local festivals such as the Western Idaho Fair. Sun Valley buzzes with summer events, and Boise comes alive with outdoor dining, farmers’ markets, and river tubing along the Boise Greenbelt. Book accommodation well in advance, particularly near popular parks and resort areas.
What to pack: Light breathable clothing, a sun hat, high-SPF sunscreen, quality sunglasses, insect repellent, a reusable water bottle, sandals for towns and sturdy boots for trails. Evenings in the mountains can still be cool, so a light fleece is worth including.
🍂 Autumn in Idaho (September–November)
Autumn is arguably Idaho’s most scenic season. The aspen groves and cottonwoods that line river valleys turn brilliant gold, particularly in October, and the cooler temperatures make hiking supremely comfortable. The Salmon River corridor and the Wood River Valley near Hailey are spectacular for leaf-peeping drives. September still offers warm, settled weather ideal for exploring, whilst October sees the colours peak and hunting season draw visitors to the backcountry. Hot springs — scattered generously across the state — become particularly appealing as evenings cool. Crowds drop noticeably after Labour Day weekend, and rates at lodges and cabins fall with them.
What to pack: Warm layering system (thermal base, fleece, and a waterproof outer shell), waterproof trousers, sturdy ankle-supporting boots, gloves, a warm hat, and a headtorch for early sunsets. Hunter orange is advisable if venturing into backcountry areas during hunting season.
❄️ Winter in Idaho (December–February)
Idaho is a seriously underrated winter destination. Sun Valley near Ketchum is one of America’s finest ski resorts, with over 2,000 acres of terrain and a glamorous yet laid-back atmosphere. Schweitzer Mountain in the north and Bogus Basin near Boise offer excellent skiing at more accessible price points. Beyond the slopes, winter reveals a quieter, more intimate Idaho: snowshoeing through silent pine forests, soaking in natural hot springs with snow falling around you, and staying in cosy backcountry lodges. Temperatures range from -5°C to 5°C in valleys, colder at altitude. Roads at lower elevations remain largely manageable with appropriate tyres, though mountain passes require chains or all-wheel drive.
What to pack: Thermal base layers (top and bottom), a quality insulated mid-layer, a heavy waterproof and windproof outer coat, ski trousers if skiing, waterproof snow boots with good grip, thick wool socks, gloves or mittens, a warm hat covering the ears, hand and foot warmers, and UV-protective goggles or sunglasses for snow glare.
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