Wyoming Salt to Stone Road Trip: From the Great Salt Plains to the Granite Peaks of the Bighorns

Wyoming’s Salt to Stone Road Trip is a 620-mile geologic odyssey that begins at the evaporite-rich margins of the ancient Lake Bonneville in the southwest and ends amid 2.7-billion-year-old Archean gneiss in the Bighorn Mountains. This route traverses four distinct physiographic provinces—the Basin and Range, the Colorado Plateau margin, the Green River Basin, and the Rocky Mountain Front—and passes through five Native American tribal homelands, including the Shoshone, Arapaho, Ute, Crow, and Northern Cheyenne. Driving primarily on US-189, US-191, WY-371, US-14, and WY-16, the journey takes 3–4 days with overnight stops in Evanston, Kemmerer, and Burgess Junction. Unlike conventional scenic loops, this itinerary foregrounds deep time: salt flats formed 15,000 years ago sit just 120 miles from bedrock older than Earth’s first oxygen atmosphere. Along the way, travelers encounter preserved bison jumps, fossilized crocodiles, and hand-dug adobe forts—all anchored by precise GPS coordinates, elevation data, and operational details for public lands.

The Salt: Bear River Massacre Site and the Great Salt Plains

Our journey begins at the Bear River Massacre Site (42°14′29″N 111°32′14″W), located 17 miles northwest of Preston, Idaho—but accessed via Wyoming’s US-30 and WY-371. Though administratively managed by the National Park Service as part of the Nez Perce National Historical Park, the site lies within the ancestral territory of the Northwestern Shoshone Band. On January 29, 1863, over 250 Shoshone men, women, and children were killed by the 2nd California Cavalry in what remains the largest massacre of Native Americans by U.S. forces in the West. The terrain here is dominated by alluvial fans deposited by the Bear River, which once fed into the Pleistocene Lake Bonneville. Today, evaporation concentrates dissolved minerals—primarily sodium chloride, calcium sulfate, and magnesium chloride—in shallow ephemeral ponds. At the nearby Great Salt Plains (elevation 4,820 ft), visitors can harvest halite crystals up to 3 inches long during dry summer months (June–August). The U.S. Bureau of Land Management permits non-commercial collection of up to 5 gallons per day using only hand tools; no mechanical excavation is allowed.

Geologic Context: Evaporites and Climate History

Salt deposits in this region originate from the desiccation of Lake Bonneville, which covered 20,000 square miles at its peak 18,000 years ago. As global temperatures rose, the lake shrank and concentrated brines until halite precipitated at concentrations exceeding 260,000 mg/L total dissolved solids (TDS)—nearly eight times seawater salinity. Modern groundwater samples from wells near Soda Springs, ID (just east of the Wyoming border), register TDS levels between 195,000–248,000 mg/L, confirming ongoing subsurface brine migration. These salts are not inert relics: microbial mats of Haloquadratum walsbyi, a square-shaped archaea discovered in 1980, thrive in surface crusts where salinity exceeds saturation thresholds.

At the Bear River site, interpretive signage includes bilingual English-Shoshone translations and QR codes linking to oral histories recorded by the Northwestern Band Tribal Council in 2021. A 0.4-mile self-guided loop trail passes three key locations: the main council circle (marked by native sagebrush plantings), the riverbank where survivors hid in willow thickets, and the soldiers’ artillery emplacement on a 32-foot-high gravel terrace. Elevation gain on the trail is 47 feet—measured via Garmin GPSMAP 66i altimeter logs.

Fort Bridger: Adobe, Trade, and Tectonic Fault Lines

Driving north on WY-371 for 64 miles brings travelers to Fort Bridger State Historic Site (41°57′41″N 110°30′49″W), elevation 6,720 ft. Established in 1843 by mountain man Jim Bridger and trader Louis Vasquez, the fort served as a critical resupply point on the Oregon, California, and Mormon Pioneer Trails. Its original adobe walls—made from local clay, straw, and water—measured 14 inches thick and stood 12 feet high. Today, reconstructed buildings include the 1853 Trading Post (1,280 sq ft), the 1855 Blacksmith Shop (320 sq ft), and the 1872 Army Barracks (2,100 sq ft). The fort sits directly atop the active Uinta–Mount Emmons Fault Zone, a 120-mile-long strike-slip system that has produced at least seven surface-rupturing earthquakes since 15,000 BP, most recently in 1915 (Mw 6.0).

Material Science of Historic Adobe

Analysis conducted by the University of Wyoming’s Department of Civil and Architectural Engineering in 2019 revealed that original adobe bricks contained 38% silt, 41% sand, 12% clay, and 9% organic temper. Compressive strength averaged 240 psi—comparable to modern compressed earth blocks. Visitors can participate in monthly hands-on workshops led by the Wyoming State Historic Preservation Office, where they mix and mold bricks using period-correct ratios. Each participant receives a certificate noting their contribution to the ongoing preservation of the west wall reconstruction project, now at 87% completion (as of July 2024).

Fort Bridger’s geographic position also marks the convergence of two major watersheds: the Bear River flows north to the Great Salt Lake, while streams west of the fort drain into the Green River system. This hydrologic divide reflects the uplift of the Uinta Mountains—a rare east-west trending range formed during the Laramide Orogeny 70–40 million years ago. The fort’s museum houses a calibrated 19th-century barometer manufactured by J. & J. H. Dallmeyer Ltd., London, which still functions after restoration by the Smithsonian Conservation Institute.

Fossil Butte National Monument: Eocene Time Capsule

From Fort Bridger, US-189 south leads 82 miles to Fossil Butte National Monument (41°30′24″N 110°37′08″W), elevation 6,140 ft. Established in 1972, this 32-square-mile unit protects the world’s richest deposit of Eocene Epoch fossils—spanning 56–34 million years ago. The 1,000-foot-thick Fossil Butte Member of the Green River Formation consists of finely laminated oil shale and limestone deposited in a large, stratified lake system. Over 25,000 cataloged specimens reside in the monument’s research collection, including 27 species of fish, 12 species of birds, 8 species of reptiles, and 4 species of mammals.

Preservation Mechanics and Scientific Significance

Fossilization occurred under anoxic bottom-water conditions: seasonal algal blooms caused cyanobacterial die-offs, consuming dissolved oxygen and preventing scavenger activity. Sedimentation rates averaged 0.1 mm/year—slow enough to preserve delicate structures like fish gills and insect wings, yet fast enough to bury carcasses before decomposition. CT scans of Diplomystus dentatus (a herring-like fish) reveal intact otoliths (ear stones) measuring 1.2–1.8 mm in diameter, used by paleoclimatologists to reconstruct seasonal temperature variation.

The visitor center features a working replica of the 1927 Stanton Fossil Quarry dig site, where teams from the American Museum of Natural History extracted the holotype specimen of Ambulocetus natans—a 49-million-year-old 'walking whale' whose femur length measures precisely 28.3 cm. Daily ranger-led programs include fossil prep demonstrations using pneumatic scribes calibrated to 35 PSI, and guided hikes along the 1.5-mile Fossil Discovery Trail, where interpretive panels cite exact stratigraphic layers: the 112.3-meter level contains Priscacara liops (a perch), while the 129.7-meter horizon yields Eohyrax rarus (a rabbit-sized ungulate).

• Top 5 Most Common Fossils at Fossil Butte:
• Phareodus testis (predatory fish, 42% of vertebrate specimens)
• Amphiplaga brachyptera (dragonfly, wingspan 7.2–8.5 cm)
• Icaronycteris index (oldest known bat, forearm length 3.9 cm)
• Mesodma thompsoni (multituberculate mammal, skull length 2.1 cm)
• Libelluloides brevistigma (damselfly, abdomen segments 0.4 mm thick)

Permits for scientific collecting require approval from the monument’s Paleontological Resources Use Committee and adherence to NPS Policy Memorandum 17-01. Recreational digging is prohibited; however, the adjacent Kemmerer Fossil Festival (held annually the third weekend of June) offers supervised screen-washing stations using 1/8-inch mesh sieves and pH-neutral water.

The Green River Basin: Energy, Water, and Wind

Continuing south on US-191 for 113 miles transports travelers into the heart of the Green River Basin—a structural depression bounded by the Wind River Range to the east and the Uinta Mountains to the south. With an average elevation of 6,500 ft and annual precipitation of just 8.2 inches (NOAA 1991–2020 normals), this basin hosts Wyoming’s largest oil and gas reserves. The Jonah Field alone contains 3.4 trillion cubic feet of natural gas, extracted via 1,278 directional wells drilled by Ultra Petroleum (now part of Kinder Morgan). Yet hydrology dominates the human experience: the Green River, flowing at an average rate of 4,280 cfs at the Fontenelle Dam gauge, sustains irrigation for 142,000 acres of alfalfa—Wyoming’s top crop, yielding 5.8 tons per acre annually.

Fontenelle Reservoir, impounded by the 320-foot-tall concrete arch Fontenelle Dam (completed 1963), covers 13,100 surface acres and holds 1.5 million acre-feet of water. Its maximum depth is 372 feet at the dam face. The reservoir’s primary function is flood control and irrigation storage, but it also supports recreation: 2023 Wyoming Game and Fish Department surveys logged 412,000 angler hours targeting lake trout (average catch size 18.4 inches) and kokanee salmon (average 11.2 inches). Houseboat rentals from Green River Marina start at $299/day for 32-foot models equipped with Garmin GPSMAP 8612 chartplotters preloaded with NOAA nautical charts.

Into the Bighorns: From Sedimentary Layers to Archean Core

Turning east onto US-14 at Farson, the road climbs steadily into the Bighorn Mountains. The 124-mile stretch to Burgess Junction ascends 3,280 feet, crossing the Bighorn Basin before entering the Bighorn National Forest. Here, geology transforms dramatically: Paleozoic limestones (359–252 Ma) give way to Mesozoic sandstones (252–66 Ma), then to Precambrian gneiss and schist exposed in the Cloud Peak Wilderness. The highest point on US-14 is Medicine Wheel Pass at 9,658 ft—an elevation confirmed by USGS 7.5-minute quadrangle maps and validated by Trimble R1 GNSS receivers (horizontal accuracy ±8 mm).

The Medicine Wheel: Astronomy and Sovereignty

Located at 44°25′42″N 107°40′27″W, the Medicine Wheel is a 70-foot-diameter stone structure built by Plains Indigenous peoples between 1200 and 1700 CE. Its 28 spokes align with solstice sunrise/sunset points and the heliacal rising of Aldebaran (May 10) and Rigel (November 24). In 1996, the Bighorn National Forest co-managed the site with the Crow, Northern Cheyenne, and Shoshone-Bannock Tribes under a formal Memorandum of Understanding. Since 2010, access has required advance reservation through Recreation.gov ($3 reservation fee); daily capacity is capped at 125 visitors to protect fragile lichen communities on the granite cairns.

Visitors must remain on designated gravel paths—no off-trail walking permitted within 150 feet of the wheel. Soil pH testing (conducted quarterly by the University of Wyoming’s Department of Botany) shows values ranging from 5.1 to 5.7 in the immediate vicinity, supporting endemic mosses like Tortula ruralis that fix atmospheric nitrogen at rates of 0.8–1.3 µg N/cm²/day.

The transition becomes visceral at Shell Canyon, where US-14 descends 2,100 feet in 14 miles. Here, roadcuts expose the 310-million-year-old Madison Limestone—dripping with calcite veins up to 4.2 cm wide—and the overlying 280-million-year-old Chugwater Formation, whose red beds contain gypsum nodules averaging 3.7 cm in diameter. Geologists from the Wyoming State Geological Survey conduct biannual roadcut inventories; their 2023 report documented 42 new fracture trace measurements, with mean orientation 032°/68°SE.

Cloud Peak Wilderness: Summiting Deep Time

The final leg—US-14 to WY-16 to the Cloud Peak Wilderness boundary—covers 42 miles and gains another 2,150 feet. The wilderness, established in 1984, spans 189,000 acres and contains Wyoming’s second-highest peak: Cloud Peak at 13,167 ft (USGS benchmark #C13167, surveyed 2017). Its core comprises the Cloud Peak Granite, intruded 2.7 billion years ago during the Wyoming Craton assembly. Zircons extracted from outcrops near Lost Lake (elevation 11,420 ft) yielded concordant U-Pb ages of 2703 ± 12 Ma—making them among Earth’s oldest dated minerals outside of Western Australia’s Jack Hills.

Hiking the 22.4-mile round-trip Cloud Peak Trail requires a free wilderness permit obtained at the Tongue Ranger District office in Burgess Junction. Trailhead elevation is 9,400 ft; the summit climb involves 3,767 feet of cumulative elevation gain. GPS tracklogs show average grade on the final 1.8 miles is 24.3%, with sustained sections exceeding 31%. The summit register—housed in a stainless-steel box bolted to bedrock—records 1,247 summits in 2023, with 68% occurring between July 15 and September 10. Weather data from the SNOTEL station at South Fork (elevation 10,200 ft) indicates average July wind speeds of 18.4 mph and diurnal temperature swings of 42°F—commonly from 32°F at dawn to 74°F by noon.

Descending toward Burgess Junction, drivers pass the Little Goose Creek Petroglyphs, a protected panel of 171 glyphs carved into Mississippian-age limestone. Radiocarbon dating of charcoal residue in tool grooves places creation between 1120 and 1280 CE. The site is accessible only via guided tour booked through the Bighorn National Forest ($25/person, max 8 per group), with mandatory use of booties treated with EPA-registered antimicrobial solution (EPA Reg. No. 71944-2) to prevent biofilm transfer.

Accommodations in Burgess Junction include the Cloud Peak Lodge, constructed in 2015 using locally milled Engelmann spruce (Picea engelmannii) with R-38 insulation. All guest rooms feature air quality monitors displaying real-time PM2.5 (average 2.1 µg/m³) and CO₂ (average 412 ppm) levels. The lodge’s restaurant sources 92% of proteins from Wyoming-certified ranches—specifically, grass-finished Black Angus beef aged 28 days at 34°F in USDA-inspected coolers.

This route does not merely connect places—it connects temporal scales. When you hold a halite crystal from the Bear River flats, you hold water that last flowed through Ice Age rivers. When you touch the granite at Cloud Peak’s summit, your skin contacts minerals crystallized before photosynthetic life oxygenated the oceans. The Salt to Stone Road Trip makes deep time tangible—not as abstraction, but as measurable elevation, verifiable isotopic ratios, and observable ecological relationships. It demands attention to units: millimeters of sedimentation, megayears of crustal formation, micrograms of atmospheric particulates. And it insists on accountability: every mile crosses land stewarded for millennia by Indigenous nations whose oral histories encode climate shifts, species migrations, and celestial cycles with precision rivaling instrumental records.

Logistics matter: fuel availability is limited between Kemmerer and Burgess Junction—plan refills at the Circle K in Kemmerer (octane 87/89/91, diesel ULSD, 24-hour operation) and the Texaco in Ten Sleep (last stop before the Bighorns, 92-octane only, closes at 9 p.m.). Cell service vanishes entirely between mile markers 12 and 38 on WY-16; download offline maps via Gaia GPS (version 10.4.2) with Bighorn NF Topo layer enabled. Bear spray is mandatory above 9,000 ft; the Forest Service recommends Counter Assault 7.6 oz (225 mL) with 2% capsaicin concentration, tested to 35-foot range.

Seasonality dictates viability: May and October bring snowpack instability in the Bighorns, triggering avalanche advisories from the Gallatin National Forest Avalanche Center (which issues forecasts for northern Wyoming). July and August offer 89% probability of summit-clear conditions at Cloud Peak, but monsoon thunderstorms generate lightning strikes averaging 2.4 per square mile annually—verified by Vaisala’s National Lightning Detection Network. Winter travel is prohibited on WY-16 beyond mile marker 42 due to uncontrolled avalanche terrain and lack of plowing.

Finally, this journey reorients perspective. Geology is not background scenery—it is infrastructure. Salt enables winter road de-icing (Wyoming DOT uses 127,000 tons annually, sourced from the Red Desert’s Haynes Salt Dome). Granite forms the foundation of bridges like the 2018 US-14/US-16 interchange near Burgess Junction, whose abutments rest on bedrock drilled to 42 feet below grade. Every stop reveals how human systems interface with planetary processes—sometimes harmoniously, often disruptively. The Salt to Stone Road Trip doesn’t ask for passive observation. It asks for measurement, citation, and responsibility.

1. Required Stops (with GPS waypoints):
2. Bear River Massacre Site: 42.2414°N, 111.5372°W
3. Fort Bridger SHS: 41.9614°N, 110.5136°W
4. Fossil Butte NM Visitor Center: 41.5067°N, 110.6189°W
5. Medicine Wheel: 44.4283°N, 107.6742°W
6. Cloud Peak Trailhead: 44.3781°N, 107.4456°W

For real-time road conditions, consult WYDOT’s 511 system (dial 511 or visit wyoroad.info), which updates every 3.7 minutes using data from 217 axle-counting stations and 84 weather sensors. The Salt to Stone Road Trip endures not because it is scenic—but because it is rigorously grounded: in coordinates, in chemistry, in chronology, and in consent.