The scene where Marty and Doc check out the unfinished bridge, they say the ravine's name is Carson ravine.

After they saved Clara Clayton, they realised she was meant to die and thats how the name was meant to be changed to Clayton Ravine.

Near the end of the film where Marty comes back to 1985, you see the sign saying "Eastwood Ravine" as in, since Marty McFly called himself Clint Eastwood, the people in 1885 must of thought he died in the ravine when the train flew off the bridge.