Living in the D.C. area, almost everywhere is a historical site, which is often maintained by the National Park Service.
Historical sites and ghosts seem to go hand-in-hand between the familiarity of it with their often unchanged, restored interiors and exteriors, and the long history of the site itself. As the NPS maintains many sites such as Hampton Mansion in Townson, MD and the Old Stone House in Georgetown, they do not have a stance on the hauntings and ghosts within them. As their public affairs rep once told me: "It's not considered scientific, so I suppose it is that we don't believe in them. I got a blank look when I asked that question. I suppose we don't have one!" I think it has a lot to do with it being a government entity. Anyone have any insight into this?