Sonderbund westdeutscher Kunstfreunde und Künstler
The "Sonderbund" — as it is normally called; its complete name being Sonderbund westdeutscher Kunstfreunde und Künstler (the "Separate League of West German Art Lovers and Artists") — was a "special union" of artists and art lovers, established 1909 in Düsseldorf and dissolved in 1916. In its first years, the Sonderbund mounted some landmark exhibitions, successfully introducing French Impressionist, Post-Impressionist and Modern Art to the western parts of Germany.
The international movement of Secessionism, which since 1890 began to cover the European art scene, entered Düsseldorf, its renowned art school and artist societies at a very late date. In 1908, a group of younger artists first organized a "special exhibition" ("Sonderausstellung"), the year following they reunited in a "Sonderbund" exhibition works of their own with French contemporary art lent by local collectors and the Galerie Bernheim Jeune of Paris. Encouraged by museum professionals, in August 1909 the Sonderbund was officially established.
The lasting fame of the "Sonderbund" is founded on its three "International Art Exhibitions", 1910 and 1911 in Düsseldorf, 1912 in Cologne, and especially on the latter exhibition, which supplied a breathtaking review of early modern art: Vincent van Gogh, Paul Cézanne, Paul Gauguin, Pablo Picasso and the neo-impressionists Henri-Edmond Cross and Paul Signac, the first generation was set in context to more recent efforts all around Europe, with a special focus on Edvard Munch.
The organizers of the 1913 Armory Show were highly impressed by the exhibition in Cologne, and thus first rate European art soon made its way to the United States.
Magdalena M. Moeller: Der Sonderbund. In: Düsseldorf. Eine Großstadt auf dem Weg in die Moderne. Der westdeutsche Impuls 1900-1914, Kunstmuseum Düsseldorf 1984, p. 126-142