Sand Mountain is a singing sand dune 20 mi east of Fallon, Nevada along U.S. Route 50. The dune is two miles long and 600 ft high. The sand originates from the ancient Lake Lahontan, that for the most part dried up 9,000 years ago. Sand Mountain Recreation Area is managed by the Bureau of Land Management and is open to off-highway vehicle use. The area is also the only home of the critically imperiled Sand Mountain blue butterfly. The ruins of the Sand Springs Station of the Pony Express are also located within the recreation area. Sport activities such as sandboarding and sand skiing can be practiced at the site.