The name Algodones Dunes refers to the entire geographic feature, while the administrative designation for that portion managed by the Bureau of Land Management is the Imperial Sand Dunes Recreation Area (sometimes called the Glamis Dunes). The Algodones Sand Dunes are the largest mass of sand dunes in California. This dune system extends for more than along the eastern edge of the Imperial Valley agricultural region in a band averaging in width. A major east-west route of the Union Pacific railroad skirts the eastern edge. The dune system is divided into 3 areas. The northernmost area is known as Mammoth Wash. South of Mammoth Wash is the North Algodones Dunes Wilderness established by the 1994 California Desert Protection Act. This area is closed to motorized use and access is by hiking and horseback. The largest and most heavily used area begins at Highway 78 and continues south just past Interstate 8. The expansive dune formations offer picturesque scenery, a chance to view rare plants and animals, and a playground for ATV and off-roading enthusiasts. The dunes are also popular in film-making and have been the site for movies such as Return of the Jedi.