Dukes of Pszczyna Archives is a location where materials are stored documenting Upper Silesia’s political, cultural and economic relations. A part of the documentation dates back to the medieval ages, especially the beginning of 16th century. Sections I, II and III of the collection contain, among others, source materials produced in connection with activities conducted in estates owned by Promitz family - Pszczyna, and Żary and Trzebiel estates in Lower Lusatia. Promintz family, related to Piasts, Kurtzbachs and Lesser Poland’s branch of Zborowscy, was in possession of the lands in years 1558-1765. Żary and Trzebiel estate was smaller than Pszczyna and slightly less well developed. Nevertheless, Erdmann II’s main residence was in Żary, and this was the place where family archives were stored as well. The documents preserved up to this date allow for detailed examination of the history of Żary and Trzebiel estate. Property deeds, wills, family documents and correspondence allow the researcher to reproduce the inner structure that governed Lusatian estates from the 16th to the second half of 18th century. By doing so one would be able to comprehensively characterize changes of the governmental structure and economic policies employed by this prominent aristocratic family.