So, the lead up to the story is that a skinwalker drags injured people into the deep forest and nails them to trees before summoning a demon into each of them, leaving them there as parasites who followed the Christians, until needed. Around the same time, a fugitive from the law takes refuge in the town that is having the abductions.
For this story to work, it has to be mostly isolated, but we're in the 60s man. The world and country, think U.S., is more and more connected. It's harder to hide anything supernatural. In Lovecraft's works, there was even the raid on Innsmouth in the 20s, one of the classic inspirations for the story.
How do I keep this area hidden away and isolated?
Note: It can't and shouldn't be completely isolated. The fugitive got there via road, and part of the point is humans are encroaching on the skinwalker's lands. But, it is mostly rural and local both in culture and economy. It can 'lag behind a bit' but should be consistent with the times.