Established in 1956, although its origins date back to the activities of the 19th-century Museum Society, the Historical Archives Celje collect and and keep records of the archives of organisations and institutions of local and regional interest.
From 1961 to 2001 the archives were housed at the Prothasi Mansion, but nowadays they are housed in new modern premises. The holdings of the Historical Archives Celje include archives dating from the 13th century to the 90's of the 20. century, the vast majority of which were created after 1850. The registers hold some 8.000 linear metres and around 1500 fonds and collections of material on various fields, including government, jurisdiction, economy, education, medicine, associations and social organisations and individuals… Its remit includes the state administrative units: Brežice, Celje, Hrastnik, Krško, Laško, Mozirje, Sevnica, Slovenske Konjice, Šentjur, Šmarje pri Jelšah, Trbovlje, Velenje, Zagorje ob Savi and Žalec. The Historical Archives Celje has cooperated successfully with the archives from the region and made several projects with archives and museums form Slovenia, Croatia, Serbia, Bosnia and Herzegovina, Austria... Archive is continously working on projects which are making cultural heritage more accessible to public.