- "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 consults the railroad map in 1885
- "There were three sonic booms, and three flashes of brilliant light. And the DeLorean was traveling across the bridge. Except now the bridge was whole. Marty glanced down at the digital display, and saw that the current year was 1985. He was home. / The DeLorean coasted on to solid ground on the far end of the bridge, the friction of the metal railroad wheels slowing the car now that there was no longer a locomotive pushing it from behind. Marty was surprised how relieved he was to see the good old world of Hill Valley — his Hill Valley — one more time. The car was passing the cliff road, now. Wait a minute! The historic Clayton Ravine sign had changed. The new sign said it was called the Eastwood Ravine now — Marty winced — named after some big locomotive wreck in 1885. The DeLorean was moving too fast for him to read any more, but that was enough. He just hoped his time traveling hadn't changed anything else in 1985."
- —From Back to the Future Part III by Craig Shaw Gardner (quote, pages 201 and 202)
Shonash Ravine, later known as Clayton Ravine (and, because of an alteration of the timeline, renamed Eastwood Ravine instead of Clayton Ravine) was a deep gorge 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 1886 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" (from his 1985 perspective), mainly because students wished that some of their teachers would fall into the ravine. In preventing this tragedy, Doc and Marty caused the site to keep the name 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 alias, "Clint Eastwood".
In the 1986B timeline, First Citizen Brown had a secret lab near the ravine (which became Clayton Ravine again). He kept the damaged DeLorean time machine there for safe keeping, but after the events of 1986C, it was known as Eastwood Ravine again.
- 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 would not 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 by jumping off the ravine 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.