M207 The Hill House, Helensburgh

This large, detached, family house stands on an elevated site overlooking the Firth of Clyde in the commuter town of Helensburgh. Built for the Glasgow publisher Walter W. Blackie, it was Mackintosh's most important domestic commission, and from the beginning its refinement and sophistication have earned it international fame as one of the outstanding houses of the 20th century. In 1972 it was bought by the Royal Incorporation of Architects in Scotland, who opened it to the public and converted the service wing into flats. Since 1982, it has been run as a house museum by the National Trust for Scotland.

Authorship: The client's own testimony, along with numerous contemporary published sources, identify Mackintosh as the architect.