A celestial sky reserve of international Gold Level acclaim. Craters that looked like they fell off the moon. A rodeo on the Professional circuit. Timeless mining history. These are but a few of the amazing attractions you’ll find in the Lost River Valley, tucked snuggly under the majestic Lost River Mountain Range looming overhead. It’s called the Lost River Valley because the Big Lost River comes tumbling down out of the mountains before it robustly makes its way through the craggy terrain.  When it reaches the Snake River Plain, the river makes a loop through the marsh and, like Houdini, promptly disappears into the porous basalt left behind by the last volcanic eruption in the region.

This is the same eruption that lifted Mount Borah, Idaho’s highest peak on the bucket list of many climbers, right up the road from the quaint western towns of Mackay and Arco. The two towns also lie right at the edge of the Gold Level Dark Skies Reserve. Traveling a bit further on the Peaks to Craters Scenic Byway takes you to Craters of the Moon National Monument. Because the volcanic rock at Craters is young, domes, cinder cones, shields, lava flows, lava tubes, spatter ramparts, and pressure ridges formed by the molten lava, still cover the area. It is expected to erupt again within the next 1,000 years, coming behind the last geologic event that occurred about 2,100 years ago.

When you visit the Lost River Valley, you’ll discover there are at least 20 other natural attractions, great hiking, world-class fishing, and exhibits related to the development of atomic energy in America. In winter, you can savor the quiet of the forest cross-country skiing or the roar of the snow machine, traversing the mountain trails. If you enjoy riding ATVs, this area is also the ATV Capital of the West. Five trails that pass through the astounding landscape, take you through the region.

Plan to visit for more than a day; there’s just too much to enjoy not to. Discover the unique region we call the Lost River Valley, a place like no other in America.

In an area first settled by cattle and sheep ranchers, the founding of Idaho Falls coincided with the gold rush of the 1860s. A ferry across the Snake River led the way to a log toll bridge, enabling settlers to move north and west, prospectors and miners seeking riches in the gold fields of Idaho and ultimately connecting to copper mining in Montana. Homesteaders from Utah brought irrigation know-how, developing a canal system fed by the Snake River. Tens of thousands of acres of desert were turned into green farmland and Idaho Falls became one of the most productive agricultural regions of the United States. The city once again made a name for itself when the Idaho National Laboratory established the National Reactor Testing Station in the region in an isolated location where various kinds of nuclear reactors were tested—52 in all.

A 13-stop self-guided walking tour includes the Willard Arts Center/Colonial Theater, Actors Repertory Theatre of Idaho, and, of course, the Idaho Falls Public Library, all on the National Register of Historic Places. 

The tour begins at 246 West Broadway

The largest museum in the state, the Museum of Idaho’s exhibits include items linked to the Lewis and Clark expedition, a re-created 1800s town, and collections and programs focused on Idaho’s social and environmental history and the Intermountain West.

200 North Eastern Avenue, Idaho Falls, ID 83402, 208-522-1400, M-Sat 10AM-6PM, Sun 1PM-5PM, Adult $13

The only art museum in eastern Idaho showcases eclectic and contemporary works by Idaho artists in five galleries, a children’s interactive art learning area, an art classroom/workshop area, and a gift shop.

300 South Capital Avenue, Idaho Falls, ID 83402, 208-524-7777, Tu-F 10AM-5PM, Sat 10AM-4PM, Adults $4 

Plan to drive on US 20/26 towards Arco to visit Experimental Breeder Reactor No. 1 (EBR-I). Colorful, interactive displays also tell the story of EBR-I’s sibling, Experimental Breeder Reactor No. 2 (EBR-II), which once powered much of the site and operated with a novel closed fuel cycle. The museum also has two aircraft nuclear propulsion prototypes, a reactor control room, remote handling devices for radioactive materials, radiation detection equipment, and more. You can walk through the museum using the self-guided tour instructions or take a guided tour.

U.S. Highway 20/26 between Idaho Falls and Arco, 208-526-0050, Memorial Day weekend through Labor Day weekend, Daily, 9AM–5PM, Free

A collection of historical nuclear informational material depicts the Manhattan Project and the development of a nuclear-powered fast attack submarine, the Desert Hawksbill Sail, with its “devil” hull number 666 jutting from the ground. The conning tower is known as the “Devil Boat.” Exhibits also highlight the development of the first usable electricity at EBR-1. This area was also the location of the first Naval Reactor Station, the birthplace and training center for the Navy’s nuclear program.

440 South Front Street, Arco, ID 83213, 208-527-3770  

Surrounded by the tallest mountain peaks in Idaho, Mackay was settled in 1880, and a decade later, copper mining began. Investor John Mackay gave the mine’s general manager permission to plan any town he wished and named it after him in a show of loyalty. Along with a smelter on the Lost River, Mackay also had the Oregon Short Line Railroad build a spur from Blackfoot. Shortly after its founding, the town boasted a brick schoolhouse, two major hotels, a bank, an opera house, two churches, several lodging houses, and dozens of company-owned homes. Today, Mackay is surrounded by farms and ranches.

Housed in a restored century-old church, the Lost River Museum showcases a variety of artifacts, including mining tools, ranching equipment, vintage clothing, household utensils, railroad memorabilia, theater memorabilia, local moonshiners, and historical photographs illustrating life in the past. 

312 Capital Avenue, Mackay, 208-588-3148, Memorial Day-Sept, Sat-Sun 1PM-5PM, or by Appointment, donations accepted. 

Relics, structures, small mines, and remnants of houses in “copper city” dot the wild backcountry of Mine Hill, dating from 1879 when ore was discovered. Over the years, almost a million tons of ore have been removed from the mountain. Interpretive Sites along the 20-mile route include the Smelter Site and Hardrock Mining Exhibit, Cossack Tunnel and Compressor Building, Horseshoe Mine and Taylor Sawmill, Anderson Cabin, White Knob Townsite, Aerial Tramway Headhouse, Ausich Cabin Site, Cliff City Town Site, Cliff City Cabin, Cliff City Smelter, Shay Railroad Trestle, and the Empire Mine Ore Bin Location. Three color-coded routes for ATVs, Cars, and 4WDs graded by difficulty are available at the 14 different locations in Mackay, Arco, and Blackfoot. 

Village Inn 310 US-93, Challis, ID 83226, 208-879-2239 

Y-Inn Cafe 1200 Main Street, Challis, ID 83226 208-879-4426

Tea Cup Cafe and Bakery 200 Main Street, Challis, ID 82336 208-879-5050

Real Deal Smokehouse 810 Highway 93, Challis, ID 83226 208-369-7526

Yankee Fork preserves a mining camp established on the Salmon River, named because everyone in the party was a Yankee. Even though no gold was discovered immediately, prospectors stayed on and finally found gold in 1870. Soon after, the Yankee Fork Mining District was organized, and after the discovery of the General Custer Mine in 1876, the area began to flood with miners. By 1910, the three popular sites, Bonanza, Custer, and Bayhorse, were all but deserted. The interpretive center illustrates the area’s mining heritage through exhibits, a gold panning station, and audiovisual programs. The grounds also feature a ¼ mile trail detailing the archeological finds of a nearby Challis Bison Jump Site. 

Junction of US 93 Milepost 244.5 and Idaho 75, Milepost 244.2 Adults $2/Family $5