The Bonneville Salt Flats, Home To Utah’s Measured Mile

Bonneville Salt Flats in Utah

On our drive to Colorado, we passed through the Bonneville Salt Flats in Utah, and while I wanted to stop, the train tracks run alongside eastbound I-80 and block access to the salt flats from the rest stop. So instead, we waited for the drive home to walk out onto the famed Utah salt flats.

The Bonneville Salt Flats are a 30,000 acre expanse of hard, white salt crust on the western edge of the Great Salt Lake basin in Utah. The salt flats are about 12 miles long and 5 miles wide with total area coverage of just over 46 square miles.

  • The Bonneville Salt Flats are comprised of approximately 90% common table salt.
  • The crust is almost 5 feet thick in places near the center of the salt flats, with the depth tapering off to less than 1 inch as you get to the edges.
  • Total salt crust volume has been estimated at 147 million tons or 99 million cubic yards of salt!
  • Geologist Grove Karl Gilbert named the area after Benjamin Bonneville, a U.S. Army officer who explored the Intermountain West in the 1830s

The Measured Mile Landspeed Records

Each summer, professional and amateur teams from around the world compete for landspeed records in different vehicle classes at annual events such as Speedweek, held each August since 1949. Racetracks are surveyed and prepared with heavy drag sleds that smooth out the surface of the salt. In addition to landspeed racing, the Utah Rocket Club and the National Archery Association hold events each year.

According to a sign erected by The Goodyear Tire & Rubber Company in June 1972:

Utah’s famed measured mile is located approximately seven miles beyond the marker and rest stop along I-80 in the middle of the vast salt flats. The elevation along the course is approximately 4,218 feet.

The total length for the measured mile course varies from year to year but for recent runs, it has been laid out in a path 80 feet wide and 10 miles long with a black reference stripe down the middle. Due to the curvature of the earth, it is impossible to see from one end of the course to the other.

Timing of the world land-speed record runs is under jurisdiction of the United States Automobile Club. World land-speed record times represent an electronically timed average of two runs over the measured mile within a one hour time period — one run in each direction.

  • The first world land-speed record on the Bonneville Salt Flats was set on September 3, 1935 by Sir Malcolm Campbell. His speed was 301.13 miles per hour.
  • Craig Breedlove holds the honor of being the first man to go faster than 400 miles, 500 miles, and 600 miles per hour.
  • Breedlove’s record of 600.601 miles per hour, set on November 15 1965, was finally broken on October 23, 1970 by Gary Gabelich. Gabelich’s new record is 622.407 miles per hour.
  • Gabelich’s rocket engine “Blue Flame” and Breedlove’s jet powered “Spirit of America” used with specially designed inflatable tires, pre-tested to speeds in excess of 800 miles per hour.

Formation of the Bonneville Salt Flats

Formation of the Bonneville Salt Flats began at the end of the last Ice Age, when the waters of ancient Lake Bonneville began to recede. Lake Bonneville covered much of Utah and was almost 1000 feet deep in the area of the Salt Flats. When the fresh water slowly disappeared, large concentrations of dissolved minerals were deposited in the soil. These minerals include gypsum and halite. Potassium and magnesium are also present in smaller concentrations.

Today, ground water still flows towards the Salt Flats from the surrounding watershed. It picks up dissolved minerals along the way, and percolates up to the surface via a shallow brine aquifer. When temperatures rise, the salty water rapidly evaporates in the heat, and the minerals are left behind to form the salt crust.

The Donner Party & The Salt Flats

In 1845, John C. Fremont led an expedition through the Salt flats to find a shorter overland route to the Pacific. Promoted by Lansford Hastings the following year as a faster and easier route to California, the Hastings Cuttoff proved to be the opposite for the ill-fated Donner-Reed party of 1846.

A factor contributing to the Donner-Reed tragedy in the Sierra Nevadas was the delay the party experienced on the Salt Flats when their wagons became stuck in the thick mud found just below the thin salt crust. Abandoned wagon parts from the party were present on the flats well into the 1930s, and the wheel tracks from their wagons are still visible today at certain points along the trail.

The tragedy of the Donner-Reed Party limited extensive use of the Hastings Cutoff as an overland migration trail. However, today it is part of the federally protected California National Historic Trail.

Know Before You Go

  • The Bonneville Salt Flats are located just off of Exit 4 on Interstate 80 in Utah, just before reaching the Nevada state line. They are approximately 100 miles and 1.5 hours driving time due west of Salt Lake City. After exiting the freeway, turn right and drive north past the truck stop. Stay on the paved road as it curves to the right away from the mountains and heads east out across the mud flats. In just over 4 miles, you will come to a cul-de-sac at the end of the pavement where a BLM sign is located.
  • You can also visit the Bonneville Salt Flats at the westbound rest stop directly off I-80.
  • The salt flats are open to the public and free to visit.
  • Temperatures on the salt flats often reach over 100 degrees in summer and can go below freezing in winter. Ultraviolet radiation coming off the salt can be intense — be sure to wear sunscreen and sun protective clothing.
  • You are allowed to drive out onto the salt flats as long as the salt flats are not wet or moist and there is no standing water on the surface. Vehciles, bicycles, motorcycles, and ATVs are permitted on the salt.
  • Driving on the salt flats at night or when they are wet from precipitation can be hazardous and result in your vehicle getting stuck in the mud.
  • Be careful! You can break thru the salt crust and become stuck in deep mud if you unknowingly travel too close to the edge of the salt flats.
  • If you go out onto the salt flats on your own, let someone know where you are and when you plan to return. Getting stuck out alone on the flats is dangerous and has resulted in past fatalities.
  • Learn more about the Utah Salt Flats Racing Association.

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