Bonneville Salt Flats

The Bonneville Salt Flats, in Tooele County in northwestern Utah, are one of the most extraordinary and otherworldly natural landscapes in North America — a 30,000-acre expanse of pure white salt crust (sodium chloride) at 4,218 feet elevation at the edge of the prehistoric Lake Bonneville basin, so flat and featureless that the curvature of the Earth is visible to the naked eye.

The salt flats are the remnant floor of the ancient Lake Bonneville — a massive inland sea that covered much of Utah, Nevada and Idaho during the last ice age (the Great Salt Lake is its modern, much-diminished remnant). The Bonneville Salt Flats are world-famous as the site of more official land-speed records than any other location on Earth, including the first measured mile over 300, 400 and 600 mph (at Bonneville Speed Week, held annually in August). The Bonneville Salt Flats are a treasured natural and cultural icon of Utah.

The Bonneville Salt Flats offer walking and driving on the salt surface (the primary experience — the perfectly flat, blinding-white salt crust extending to the horizon in every direction, with the mountains ringing the basin floating above a shimmering heat mirage, is one of the most surreal landscapes in North America; visitors may drive and walk on the salt surface in the public area), photography (the reflections in thin standing water after rain, the shimmer of the heat mirage, the vehicle speed-trial lines, and the infinite white horizon are extraordinary subjects), Bonneville Speed Week attendance (held annually in August on the long salt course — one of the great American motorsport traditions, with streamliners and hot rods attempting land-speed records on the measured course), sunrise and sunset viewing (the salt glows pink and gold at the ends of the day), and stargazing (the flat horizon offers an exceptional 360-degree sky view). The sensory experience of the pure-white salt flat and the speed-week tradition are the singular draws.

Late summer (July through September) is the classic visit season — the salt surface is dry, firm and at its best for driving and walking, and Bonneville Speed Week (August) brings the salt flat to life with the land-speed-record tradition. Late fall through spring, the salt surface is often flooded by a shallow brine layer (a few inches of standing water covering the crust — creating extraordinary mirror reflections of the sky and the Pilot Range mountains, one of the most photographed phenomena at Bonneville) which is beautiful but the surface is wet and soft. Summer for the dry salt and Speed Week, and late fall through winter for the mirror-reflection flooding, each offer a distinct and extraordinary experience.

The Bonneville Salt Flats are the remnant floor of Lake Bonneville — the great Pleistocene lake that covered 19,691 square miles of the Great Basin at its maximum (roughly the size of Lake Michigan) about 15,000 years ago; as the climate dried at the end of the last ice age, the lake evaporated, leaving the salt deposits that form the flats today. The flats were first used for speed attempts by William Rishel in 1896 (bicycle) and 1900 (automobile). The formal speed-trial tradition began in 1914. The world land-speed record has been set or broken at Bonneville more times than at any other location — drivers including Ab Jenkins, Sir Malcolm Campbell (who set the first 300-mph record here), Craig Breedlove and others. The Bonneville Salt Flats are a National Natural Landmark.

The Bonneville Salt Flats are the evaporite floor of ancient Lake Bonneville — as the lake evaporated at the end of the Pleistocene, the dissolved minerals (primarily sodium chloride, with sodium sulfate and other salts) were concentrated and precipitated onto the lake floor, forming the salt crust. The salt layer is approximately 5 feet thick at the center of the flats. The crust floats on a brine layer (salt-saturated water) that underlies the entire salt flat. The crust surface is so flat that it is used as a surveying datum. The Pilot Range to the west and the Newfoundland Mountains to the east were islands in Lake Bonneville — wave-cut terraces from the ancient lake are still visible on their flanks. The salt crust has been thinning in recent decades (from potash mining upstream and changes in runoff patterns), a significant conservation concern.

The Bonneville Salt Flats support very limited wildlife due to the hypersaline soil — brine shrimp (Artemia franciscana) live in the seasonal shallow brine water, the only animal that can survive in the saturated salt brine; brine flies are abundant at the edge of the brine; shorebirds (American avocets, Wilson’s phalaropes, eared grebes) feed on the brine shrimp and flies at the water’s edge when the flats are flooded. The surrounding bajadas (alluvial fans) support standard Great Basin desert wildlife (pronghorn, coyotes, burrowing owls, horned larks, sage thrashers). The salt flat itself is biologically one of the most extreme and inhospitable environments in North America for most organisms.

The Bonneville Salt Flats are an extreme endorheic evaporite environment — one of the most saline natural environments in the United States, supporting only the most halophytic (salt-tolerant) organisms. The salt-crust thickness has been declining over the past century (the BLM has been trucking brine water back onto the flats to try to maintain the salt thickness), likely due to potash mining that has altered the subsurface brine hydrology. Maintaining the salt-crust thickness is a critical conservation challenge. The seasonal flooding and evaporation cycle is the primary ecological process. Minimizing vehicle damage to the salt crust (staying on designated driving areas) protects the crust from accelerated erosion.

The Bonneville Salt Flats hold an iconic place in American culture — the site of more land-speed records than any other location on Earth, the setting for the great American motorsport tradition of Bonneville Speed Week (since 1914), the landscape for countless car commercials, music videos and films (“The World’s Fastest Indian”, featuring Sir Anthony Hopkins), and one of the most surreal and photogenic natural environments in North America. The salt flat’s absolute flatness, its blinding whiteness and its horizon-to-horizon scale make it genuinely singular. Bonneville is a treasured natural and cultural icon of Utah and of American speed culture.

The Bonneville Salt Flats are in Tooele County, northwestern Utah, adjacent to Interstate 80 at exit 4 (about 100 miles west of Salt Lake City). The Bonneville Salt Flats International Speedway access road leads from exit 4 to the public salt flat area. The salt flat is managed by the BLM and is open year-round; the surface is accessible for walking and driving (check current surface conditions — the BLM posts condition reports). The nearest services are in the town of Wendover (5 miles west, on the Utah-Nevada border). A vehicle is required; no shuttle or public transit serves the area. Check the BLM for current surface conditions and any event closures (Speed Week in August closes the racing course).

The BLM manages the Bonneville Salt Flats. The declining salt-crust thickness is the primary conservation concern — the BLM’s Bonneville Salt Flats brine enhancement program pumps saline water onto the flats during winter to replenish the crust. Visitors help by driving only in the designated vehicle area (heavy vehicles driven across the crust damage and compact it, accelerating thinning; stay on the marked area and respect any surface closures), not collecting salt or minerals, and packing out all trash. The salt flat surface is most vulnerable when wet — check the BLM condition report before driving on the surface; driving on a wet, soft salt surface causes deep ruts that take years to self-heal.

The intense white-salt reflection creates extreme UV and glare — wear UV-protective sunglasses and sunscreen at all times on the salt flat (the reflective surface doubles your UV exposure; sunburn on the salt flat can be severe). Carry adequate water (the area is extremely arid and hot in summer; dehydration risk is high). The salt crust can be slippery when wet. Summer temperatures exceed 100°F; visit in the early morning. Do not drive fast on the public salt flat area (speed trials are conducted only on the designated racing course during permitted events). Respect the UV reflection, the heat, the slippery wet crust and the water requirements.

BLM public land; no fee. Vehicle driving permitted in the designated public area (check BLM for current surface condition and any closures). No collecting of salt or minerals. No camping on the salt flat (camp in Wendover or at designated BLM areas nearby). During Bonneville Speed Week (August) and other permitted events, portions of the salt flat are closed — check the BLM and the Southern California Timing Association (SCTA) for event schedules. Pack out all trash. Leave no trace on the salt flat. Check BLM for current surface conditions and rules before visiting.

The town of Wendover (5 miles west — a Utah/Nevada border town with casinos, hotels, restaurants and the Wendover Air Force Base WWII museum — the base from which the Enola Gay and Bockscar departed for Hiroshima and Nagasaki), the Tooele Army Depot and Dugway Proving Ground (nearby historic military sites), the Great Salt Lake (50 miles east — the modern remnant of Lake Bonneville), Salt Lake City (100 miles east — Utah’s capital), and the Nevada Great Basin desert to the west define the region. Bonneville is a genuine once-in-a-lifetime landscape worth a dedicated stop on any I-80 cross-country drive.

Visit Bonneville in late October or November after the first seasonal flooding — a few inches of brine water covers the salt flat, creating a perfect mirror of the sky and the Pilot Range to the west; on a calm, clear morning, the reflection is so perfect that the sky and salt seem to merge, and walking on the flooded surface feels like walking through the sky. Bring a wide-angle lens and a tripod for the reflection photography (the golden hour is extraordinary). For Speed Week (August), arrive on Thursday for the best variety of cars and the most open access to the pit area; the land-speed-record attempts on the long course are the most dramatic moments. Time your I-80 cross-country drive to stop here; the landscape is unlike anything else in the American West.