What's the story with this fence

I was up on Sheep Mountain today and came across this old rail fence made of fallen timbers running up the ridge. Does anyone know the history of this region. The fence looks like it could be 100 years old, but may only be 20. Who knows? I'd like to find out more. Incidentally, it's a great hike to Sheep Mountain. We'll run it in Happy Trails in Out There in a few weeks.