The cultural historian Karl Trautmann (1857-1936), the then curator of the picture collection belonging to the Historischer Verein von Oberbayern (Historical Society of Upper Bavaria), purchased the extensive estate of the painter Johann Georg von Dillis from the Dillis family for 200 German marks in 1896. This sum corresponded to the total annual budget that the society had available to expand the picture collection. According to Trautmann, this purchase brought almost 2,000 sketches by Johann Georg von Dillis and his brothers Cantius and Ignaz and the children of the latter, Franz and Anna, as well as part of Dillis' written estate to the society. The latter contains documents relating to Dillis' professional activity in the broadest sense.
The extensive collection of Dillis' watercolours and sketches, in fact there are 8,256 inventory numbers, including 40 sketchbooks, with a total of around 9,500 motifs, was always regarded as a special treasure of the Historischer Verein von Oberbayern, in addition to the works by Carl August Lebschée. It has been on permanent loan from the society to the Städtische Galerie im Lenbachhaus (Municipal Gallery at Lenbachhaus) since 1996.
Johann Georg von Dillis, who was a professor of landscape at the Münchner Kunstakademie (Munich Art Academy), gallery director and royal art consultant, was one of the most important German artists of the time around 1800. With a pencil, chalk and watercolours always at hand, he captured his impressions at every opportunity – he produced drawings, watercolours and sketches in private company, on hikes or his numerous journeys. His cloud studies are particularly outstanding, many of which are part of the historical society's holdings. As numerous sketches show, Dillis also studied historical role models such as Backhuyswn, Ruisdael, Hobbema and above all Claude Lorrain. Although his main subject was landscape painting, the artist also portrayed family members, friends and acquaintances. His character studies of hunters, farmers, craftsmen and old people are impressive.
Dillis' special merit is to have made nature observation the basis of his landscape painting. With this he became a pioneer of plein-air painting in Munich.