I'm thinking somewhere on the edge of New Englad border. There's a lot of little fishing towns that ha roots in colonial times. Possibly (depending on how historically accurate we want to be. It could be during the French and Indian war. That way if a few people disappear it won't really be noticed. Would also be a reason the coven has been getting stronger. 

I for one am a history nut but I'm fine with our making up city names and the such.