The will of John Alfred Brown (1900–1987), one of the three sons of Sidney and Jenny Brown and, like his two brothers Sidney Hamlet (1898–1970) and Harry Frank (1905–1972), childless, made it possible to establish an Impressionist and house museum at Villa Langmatt in 1990.  

In accordance with his testamentary instructions, the town of Baden established the Langmatt Museum as a foundation under private law. In memory of his parents, who had built the house in 1900–1901 and assembled the bulk of their private collection of Impressionist art between 1908 and 1919, John A. Brown named it the ‘Langmatt Sidney and Jenny Brown Foundation’. The founder’s grandfather, the Englishman Charles Brown (1827–1905), joined the Sulzer Brothers company in Winterthur as an engineer in 1851; the firm went on to become one of Switzerland’s most important engineering works. The founder’s father, the engineer Sidney William Brown (1865–1941), served as technical director and delegate of the Swiss board of directors at Brown Boveri & Cie. (BBC) in Baden until 1935. Sidney’s brother, Charles Eugene Lancelot Brown (1863–1924), and Walter Boveri (1865–1924) had founded the company in 1891. Sidney William Brown stepped down from the BBC’s board of directors in 1935 and officially retired from the company at the age of 70. During the 20th century, the BBC developed into a leading company in the field of electrical engineering. In 1988, the company merged with the Swedish firm Asea to form the https://global.abb/group/en/about/history (ABB).

Sidney William Brown was married to the art-loving Jenny Sulzer (1871–1968), the daughter of the senior partner at the Sulzer Brothers firm in Winterthur. Thanks to his inheritance and professional success, he amassed a considerable fortune at the beginning of the 20th century, which enabled Sidney and Jenny Brown to realise their vision of building a significant art collection, now held in trust for the public at the Langmatt Museum, the historic site of their former family home.

Based on the testamentary disposition of John A. Brown (1900–1987), in 1988 the city of Baden, as sole inheritor, set up the Stiftung Langmatt Sidney und Jenny Brown, with the purpose of making the Villa Langmatt, the park, and the associated collections of the Brown family accessible to the public.

§ 4 of the deed of foundation formulates the foundation’s purpose:
«The purpose of this foundation is: a) to preserve the Villa Langmatt, with its park and art collections, for the city of Baden and to make them accessible to the public; b) to honour the memory of the founding Brown family and to present the foundation’s property as they would have wished, c) to promote the understanding of art and cultural activities in the city, the region, and the canton, and, d) to preserve valuable artwork and to promote understanding of art among the general public.»