Question: Stillman House follows the demonstration that now sits at which 40-room National Trust house?

Context paragraphs:
National Trust Company: The National Trust Company was incorporated on August 12, 1898 under the name of The National Trust Company of Ontario Limited.  In 1899, with the opening of an office in Montreal, the name was changed to The National Trust Company, Limited.  In 1984, National Trust amalgamated with The Victoria & Grey Trust Company and the company once again changed its name, this time to The National Victoria & Grey Trust Company.  Because the name was deemed too cumbersome, however, it was subsequently changed to the National Trust Company on June 3, 1985.  On August 14, 1997, Scotiabank purchased the National Trust Company.

Old Shute House: Old Shute House (known as Shute Barton between about 1789 and the 20th century), located at Shute, near Colyton, Axminster, Devon, is the remnant of a mediaeval manor house with Tudor additions, today in the ownership of the National Trust.  It was given a Grade I listing on 14 December 1955.  It is one of the most important non-fortified manor houses of the Middle Ages still in existence.  It was built about 1380 as a hall house and was greatly expanded in the late 16th century and partly demolished in 1785.  The original 14th-century house survives, although much altered.  This article is based on the work of Bridie (1955), which has however been superseded as the standard work of reference on the architectural history of the building by the unpublished Exeter Archaeology Report of 2008 produced for the National Trust.  This report draws on new evidence gained from the recently discovered survey of 1559 made by Sir William Petre, which lists each main room of the then existing house together with its contents.  From this evidence a conjectural ground plan of the house pre-1785 was recently produced by Roger Waterhouse.

Watersmeet House: Watersmeet House is a National Trust property located some 1.8 mi east of Lynmouth, in the English county of Devon.  A former fishing lodge, it is today used as an information centre, tea room and shop by the National Trust.  Adjoining the house is the Watersmeet SSSI, a Site of Special Scientific Interest.

Department of Primary Industries Building: The Department of Primary Industries Building (now known as National Trust House) is a heritage-listed former public service building at 99 William Street, Brisbane City, City of Brisbane, Queensland, Australia.  Prior to its adaptation for public service offices, it operated as the William Street Immigration Depot.  It was added to the Queensland Heritage Register on 4 July 1995.

Kykuit: Kykuit ( ), known also as the John D. Rockefeller Estate, is a 40-room National Trust house in Westchester County, New York, built by order of oil tycoon, capitalist and Rockefeller family patriarch John D. Rockefeller.  Conceived largely by his son, John D. Rockefeller, Jr., and enriched by the art collection of third-generation scion, Governor of New York and Vice President of the United States, Nelson Rockefeller, it has been home to four generations of the family.

National trust: A national trust is an organisation dedicated to preserving the cultural heritage of a particular geographic region.  Although the focus of a national trust may vary by region, the principal role is to ensure the preservation of historically significant items, and to conserve areas of natural beauty.  National trusts generally operate as private non-profit organizations.  The first such trust organisation, The Trustees of Reservations, originated in 1890 as a regional group serving the state of Massachusetts, USA.  The first national trust, the National Trust for Places of Historic Interest or Natural Beauty, was founded in England in 1895 and operates as a charitable organisation serving England, Wales and Northern Ireland (it is commonly known in the UK as the National Trust).  Other national trusts have since been set up around the world.

Stowe House: Stowe House is a Grade I listed country house located in Stowe, Buckinghamshire, England.  It is the home of Stowe School, an independent school and is owned by the Stowe House Preservation Trust who have to date (March 2013) spent more than £25m on the restoration of the house.  Stowe House is regularly open to the public and can be explored by guided tour all year round or during the school holidays you can explore at your own pace with a multimedia guide.  The gardens (known as Stowe Landscape Gardens), a significant example of the English garden style, along with part of the Park, passed into the ownership of The National Trust in 1989 and are open to the public.  The parkland surrounding the gardens is open 365 days a year.  National Trust members have free access to the gardens but there is a charge for all visitors to the house which goes towards the costs of restoring the building.

Le Don Hilton: Le Don Hilton or "La Cauminne à Marie Best" is an 18th-century guard house and powder magazine that sits on the seawall besides Le Chemin de L’Ouzière, in Saint Peter, Jersey.  It is also known as "the White Cottage" because of its whitewashed walls and vault, and its distinctive appearance makes it an informal daymark for sailors.  (Admiralty Chart 1137 does not identify the building as a recognised maritime marker.)  Earlier names for the building include St. Peter’s Guardhouse and Magazine, the Middle Battery, and the Powder Magazine, among others.  Today the National Trust for Jersey, which owns the building, calls it Le Don Hilton.  The National Trust rents it out for occasions such as weddings and for overnight stays, though the facilities are minimal.

Castleward Opera: Castleward Opera was a Northern Ireland opera company which staged an annual opera festival at Castle Ward, a National Trust House near Strangford in County Down.  It was founded in 1985 by Ian Urwin and Jack Smith, with performances taking place in a converted stable on the grounds of the castle.  Following the cut to its core funding by the Arts Council of Northern Ireland, the festival saw its final opera performances in June 2009 and in September 2010 held two gala farewell concerts of highlights from the company's 25-year history.  In January 2010, a new venture, supported by the Arts Council of Northern Ireland, was proposed—Opera Company NI—which the Arts Council said would "incorporate the best resources from Castleward Opera and Opera Fringe".

Stillman House: Stillman House (1950) follows Marcel Breuer’s Gregory Ain demonstration “House in the Garden” built the year before for the MOMA Museum, which now sits at the Rockefeller Kykuit estate in Hudson Valley, NY.  The Stillman house boasts three separate architectural commissions by Breuer between 1950-1953: a main house, a studio, and pool and porch redesign, with the latter featuring an 18’x10’ pool mural wall by friend and sculptor, Alexander Calder.  During this time, fellow first-generation Bauhaus friend and artist, Xanti Schawinsky, executed an interior mural wall as well.

Supporting paragraphs: Stillman House Kykuit
Answer: Kykuit