This seems to be a bit of a shortcut...
The book "A Brief Guide to Ghost Hunting: How to Investigate Paranormal Activity from Spirits and Hauntings to Poltergeists" tells us:
> Both the Whaley House and the Winchester Mystery House are also widely reported as, rather improbably, US Department of Commerce 'certified' haunted houses. Matt Schulz, Technical Director of San Diego Ghost Hunters, contacted the US Department of Commerce regarding the certified claim. It turned out that the US Travel Service, part of the Department of Commerce, had released a brochure aimed at promoting travel to the US abroad in the late 1960s or early 1970s. Called 'Who's Whooooo', the brochure gave details of some thirty allegedly haunted locations in the US, including the Whaley and Winchester Houses.