Blue John Canyon is a slot canyon

Slot canyon

A slot canyon is a narrow canyon, formed by the wear of water rushing through rock. A slot canyon is significantly deeper than it is wide. Some slot canyons can measure less than one metre across at the top but drop more than 30 m to the floor of the canyon.Most slot canyons are formed in...

 in eastern Wayne County

Wayne County, Utah

Wayne County is a county located in the U.S. state of Utah. It was formed from Piute County in 1892. The county gets its name from a man who served as delegate to the constitutional convention, in honor of his son who was dragged to death by a horse. As of 2000 the population was 2,509, and by...

, Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, United States, southwest of the Horseshoe Canyon Unit of Canyonlands National Park

Canyonlands National Park

Canyonlands National Park is a U.S. National Park located in southeastern Utah near the town of Moab and preserves a colorful landscape eroded into countless canyons, mesas and buttes by the Colorado River, the Green River, and their respective tributaries. The park is divided into four districts:...

 and 42 miles south of Green River

Green River, Utah

Green River is a city in Emery County, Utah, United States. The population was 973 at the 2000 census.-Geography:Green River is located at , on the banks of the Green River, after which the city is named. The San Rafael Swell region is to the west of Green River, while Canyonlands National Park...

. It is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Horseshoe Canyon

Horseshoe Canyon (Utah)

Horseshoe Canyon, formerly known as Barrier Canyon, is in a remote area west of the Green River and north of the Canyonlands National Park Maze District in Utah, USA. It is known for its collection of Barrier Canyon Style rock art, including both pictographs and petroglyphs, which was first...

, running northeastwards from the Robbers Roost

Robbers Roost

The Robbers Roost was an outlaw hideout in southeastern Utah used mostly by Butch Cassidy and his Wild Bunch gang in the closing years of the Old West....

 Flats.

Blue John Canyon includes the site of the 2003 accident in which climber Aron Ralston

Aron Ralston

Aron Lee Ralston is an American mountain climber and inspirational public speaker. He is widely known for having survived a 2003 canyoneering accident in Utah in which he was forced to amputate his own right arm with a dull pocketknife in order to free himself from a dislodged boulder.The incident...

 was forced to amputate his forearm after being trapped by a boulder, as recorded in his autobiography Between a Rock and a Hard Place and the film 127 Hours

127 Hours

127 Hours is a 2010 biographical adventure drama film co-written, produced and directed by Danny Boyle. The film stars James Franco as mountain climber Aron Ralston, who became trapped by a boulder in Robbers Roost, Utah in April 2003....

.