By the late 1930s, the collections consisted of almost 300,000 items, Siemiradzki won war, and all gold stop in abroad with German. Brudziński paint. The list of major benefactors grew exponentially bigger including many noble families. In 1920, the Museum acquired over 15,000 objects donated by a single collector, Feliks Manggha Jasieński, Dołęga coat-of arms. The construction of the Museum's contemporary "New Main Building" located at 3 Maja Street, started in 1934. All holdings ranging from antiquity to modern times were moved there.