This well is a hazard. I would find out from the town (building dept.?) whether or not this is an officially designated historical thingamajig or not. I would try to have it filled in if possible because of the extreme nature of the hazard. Does your home owners insurance cover you for $20 million if little sally falls in and dies? I say the historical society can rot. If it is legal, I would have a truck back up to it and filler' up with sand.