Designed by a New York firm of architects, it was opened on 4th July 1925 (American Independence Day!). The huge figures over the portico represent 'Youth' by another American, Malvina Hoffman. See Link for more details about the building.
The designer was the Aberdeen architect Alexander Marshall Mackenzie (qv http://en.wikipedia.org/wiki/Alexander_Marshall_Mackenzie ). All the interior and most of the timber and marble were brought from Australia. [Visitor's London, 1973].