The Preservation Society of Newport County
From their about page:
"The Preservation Society of Newport County, Rhode Island's largest cultural organization, preserves and protects the best of Newport County's architectural heritage. Its 11 historic properties and landscapes - seven of which are National Historic Landmarks - trace America's architectural and social development from the Colonial era through the Gilded Age. In keeping with its mission, the Society strives to offer its members and the public a comprehensive view of each property's architecture, interiors, landscapes and social history...."
They're interested in education, research and conservation - and hosting events like weddings.
There's information for visitors - but I think the website's worth visiting for the photos, even if you won't be going to Newport.
HomeOffice of England - To Let"
(May 16, 2010)