Question: Who designed the Vanderbilt mansion that is owned and operated by the Preservation Society of Newport County?

Context paragraphs:
The Breakers: The Breakers is a Vanderbilt mansion located on Ochre Point Avenue, Newport, Rhode Island, United States on the Atlantic Ocean.  The building became a National Historic Landmark in 1994, and is a contributing property to the Bellevue Avenue Historic District.  It is owned and operated by the Preservation Society of Newport County and is open for visitation on a year-round basis.

Chepstow (mansion): Chepstow is an Italianate house museum located at 120 Narragansett Avenue in Newport, Rhode Island, US.  Built in 1860, Chepstow originally served as an early summer "cottage".  Currently, the Preservation Society of Newport County owns the property.

Joseph Rogers House (Newport, Rhode Island): The Joseph Rogers House (also known as "Robert Rogers House") is an historic house at 37 Touro Street, facing Washington Square in Newport, Rhode Island.  It is a three story wood frame structure with a hip roof.  Its main facade is five bays wide, with a center entry framed by pilasters and topped by a fanlight.  The house was built c. 1790 by Joseph Rogers, a merchant.  It remained in private hands until the 1890s, when it was adapted for use first as a convent, and then as a parochial school, by the Roman Catholic Diocese of Providence.  It was given to the Preservation Society of Newport County in 1961, and Dr. and Mrs. David Van Pelt restored the building for the Society, which used it as it headquarters.  The Society moved its headquarters to 424 Bellevue Avenue in 1992.

Chateau-sur-Mer: Chateau-sur-Mer is the first of the grand Bellevue Avenue mansions of the Gilded Age in Newport, Rhode Island.  Located at 424 Bellevue Avenue, it is now owned by the Preservation Society of Newport County, and is open to the public as a museum.  Chateau-sur-Mer's grand scale and lavish parties ushered in the Gilded Age of Newport, as it was the most palatial residence in Newport until the Vanderbilt houses in the 1890s.  It was designated a National Historic Landmark in 2006.

Pine Tree Point: Pine Tree Point was the Adirondack Great Camp on Upper St. Regis Lake of Frederick William Vanderbilt, a director of the New York Central Railroad for 61 years.  Vanderbilt maintained residences in New York City at 450 Fifth Avenue, Hyde Park ("Vanderbilt Mansion National Historic Site"), Newport ("Rough Point"), and Bar Harbor ("Sonogee").

Marble House: Marble House is a Gilded Age mansion at 596 Bellevue Avenue in Newport, Rhode Island, now open to the public as a museum run by the Preservation Society of Newport County.  It was designed by the society architect Richard Morris Hunt.  For an American house, it was unparalleled in design and opulence when it was built.  Its temple-front portico, which also serves as a porte-cochère, resembles that of the White House.

Ochre Court: Ochre Court is a large châteauesque mansion in Newport, Rhode Island, United States.  Commissioned by Ogden Goelet, it was built at a cost of $4.5 million in 1892.  It is the second largest mansion in Newport after nearby The Breakers.  These two mansions, along with Belcourt Castle (the 3rd largest mansion) and Marble House, were designed by architect Richard Morris Hunt.  It is owned by Salve Regina University.

Preservation Society of Newport County: 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 protect, preserve, and present an exceptional collection of house museums and landscapes in one of the most historically intact cities in America" --Newport, Rhode Island.  The organization also protects the architectural heritage of Newport County, Rhode Island, but most especially 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.  It was announced on January 8, 2017 that the 2016 visitation of the Preservation Society properties had surpassed 1,000,000 tours.

Kingscote (mansion): Kingscote is a Gothic Revival mansion and house museum at Bowery Street and Bellevue Avenue in Newport, Rhode Island.  Designed by Richard Upjohn and built in 1839, Kingscote was one of the first summer "cottages" constructed in Newport, and is now a National Historic Landmark.  It was later twice remodeled and extended, by George Champlin Mason and Stanford White.  It was owned by the King family from 1863 until 1972, when it was given to the Preservation Society of Newport County.

El Rio de Luz: El Rio de Luz (The River of Light) (1887) is an oil on canvas landscape by Frederic Edwin Church acquired by the National Gallery of Art in 1965.  According to the NGA, the work is a "fanciful pastiche" of the many sketches and drawings Church made while traveling in South America in 1857.  The NGA notes that "the tightly focused realism, the overall tonal harmony and restrained coloration, and the compositional unity all lend a remarkable cohesiveness to the work."  William Earl Dodge, Jr. (d. 1903) was the original owner of the work and passed it to his descendants.  In 1965, it was given to the Preservation Society of Newport County, Rhode Island, and purchased in December 1965 by the National Gallery of Art.  The painting was restored in 1988.

Supporting paragraphs: Ochre Court The Breakers
Answer: Richard Morris Hunt