"Here. This spur that runs off the main line three miles out to Clayton Ravine. It's a long stretch of level track that will still exist in 1985. This is where we will push the DeLorean with the locomotive. Funny. This map calls Clayton Ravine, Shonash Ravine. That must be the old Indian name for it. It's perfect. A nice long run that goes clear across the bridge over the ravine - you know, over near that Hilldale housing development."

—Doc Brown at the railroad map in 1885

Shonash Ravine, later known as Clayton Ravine and even later renamed Eastwood Ravine, was a ravine to the south of Hill Valley. Carson Spur led directly to the ravine and for some time simply terminated at its edge. A railroad bridge was constructed across it in Summer 1887 that led to town, near the future site of Hilldale. On September 4, 1885, Doc Brown and Marty McFly

scoped out the ravine for a plan to return Marty to 1985. In the distance they heard the screams of the new school teacher Clara Clayton whose horses had gone amok after seeing a rattlesnake. Doc and Marty saved Clara from falling into the ravine, thus changing history.

After taking Clara to her house, Marty remembered from history class that the ravine was named after a school teacher that fell in there "a hundred years ago", that year, mainly because students wished that their teachers would fall into the ravine. In preventing this tragedy, the ravine remained Shonash Ravine until Marty's temporal displacement attempt on September 7, 1885, when it was thought he fell in with the train. By 1985, the ravine was then known as Eastwood Ravine, named after Marty's 1885 name, "Clint Eastwood".

In the 1986B timeline, Citizen Brown has a secret lab near the Ravine (which became Clayton Ravine again). He kept the damaged DeLorean time machine there for safe keeping.

Theory

According to the FAQs, Shonash Ravine might have kept its original name after Doc went back to 1885, as Doc was able to keep his promise and meet Clara upon her arrival (prior to Marty's arrival to 1885). As such she wouldn't fall into the Ravine.  (As the FAQ describes it, "If Marty were to go to the ravine in 1955 at the beginning of Back to the Future Part III (on his way to the Pohatchee Drive-in, for example), he would discover that the ravine is called 'Shonash Ravine'."

The FAQ, also offers the theory that if Clara had committed suicide after Doc was killed by Buford Tannen, the sympathetic townsfolk would have renamed the landmark as Clayton Ravine anyway; Zemeckis and Gale wrote that they would "remain ambiguous about whether this suicide incident actually happened", in the answers to the FAQ.[1]

Appearances

• Back to the Future Part III
• Back to the Future Part III novelization
• Back to the Future: The Card Game (Mentioned only)
• Back to the Future: The Game
  • Back to the Future: The Game - Episode 4: Double Visions (Mentioned only)