Mothman Festival is an annual event held every third weekend of September in Point Pleasant, West Virginia — home to everyone's favorite cryptid: The Mothman!
Acadia National Park can be nice that weekend, just a little harder to find places that are open. Much of the tourism completely shuts down mid-October after peak foliage. But the park is still gorgeous and mostly empty.
I second Salem. They definitely embrace the halloween thing and it's pretty fun. Also some places take Oktoberfest pretty seriously up there and those can be pretty fun.