Justin K. Thannhauser (1892–1976) was an important figure in the development and dissemination of modern art in Europe. From an early age he assisted his father, art dealer Heinrich Thannhauser (1859–1935), in the management of his renowned Moderne Galerie, which was founded in Munich in 1909. Together the Thannhausers built an impressive and versatile exhibition program that included the French Impressionists and Post-Impressionists, the Italian Futurists, and regularly featured contemporary German artists. The Moderne Galerie presented the premier exhibitions of the New Artists’ Association of Munich (Neue Künstlervereinigung München) and The Blue Rider (Der Blaue Reiter), both of which included Vasily Kandinsky, in 1901 and 1911, respectively. The gallery also mounted the first major Pablo Picasso retrospective in 1913, thus initiating the close relationship between Justin K. Thannhauser and Picasso that lasted until the artist’s death in 1973.

Following World War I, Thannhauser succeeded his father in the management of the gallery and created new branches in Lucerne (1919), with his cousin Siegfried Rosengart (1894-1985), and Berlin (1927). In the 1930s the business operations of the Thannhauser galleries were hindered by a Nazi government bent on purging the so-called degenerate art of the avant-garde. The Galleries Thannhauser officially closed in 1937, shortly after Thannhauser and his family immigrated to Paris. Thannhauser eventually settled in New York in 1940 and, together with his second wife, Hilde (1919–1991), established himself as a private art dealer.

The Thannhausers’ promotion of artistic progress, and their advancement of the early careers of such artists as Kandinsky, Franz Marc, and Paul Klee, paralleled the vision of the Guggenheim Museum’s founder, Solomon R. Guggenheim (1861–1949). In recognition of this shared spirit, and in the memory of his first wife and two sons, who might have continued in the family’s art trade had they not died at tragically young ages, Justin Thannhauser bequeathed in 1963 the essential works of his collection to the Guggenheim Foundation. The director of the museum at that time, Thomas M. Messer, played a critical role in securing the bequest, having been acquainted with Thannhauser since the early 1950s.  From 1965 until Thannhauser’s death in 1976, the works were placed on loan to the museum and housed in the newly dedicated Thannhauser Wing in the second floor of the Guggenheim’s Monitor building. The collection was legally transferred to the foundation in 1978. Hilde Thannhauser subsequently made several additional gifts, including a bequest of ten works upon her death in 1991.

The Thannhauser gift significantly expanded the historical range of the Guggenheim’s collection, providing an important survey of the period directly antedating that represented by the museum’s original holdings, the Guggenheim could now represent the trajectory of Modern art from its beginnings in the nineteenth century. Included in the Thannhauser Collection are such incomparable masterpieces as Vincent van Gogh’s Mountains at Saint-Rémy, Edouard Manet’s Before the Mirror, and Camille Pissarro’s The Hermitage at Pointoise. The gift also greatly enhanced the museum’s collection of Picasso, with close to 30 paintings and drawings by the Spanish master, among them such seminal works as Le Moulin de la Galette and Woman Ironing.