The Preservation Society of Newport County is a private, non-profit organization based in Newport, Rhode Island. It is Rhode Island's largest and most-visited cultural organization. The organization's mission is to preserve the architectural heritage of Newport County, Rhode Island, including those of the Bellevue Avenue Historic District. Its fourteen historic properties and landscapes—seven of which are National Historic Landmarks, and eleven of which are open to the public—form a complete essay of American historical development from the Colonial era through the Gilded Age.