Siewierz was ruled by the Silesian Piasts as part of the Duchy of Bytom under Duke Casimir. In 1312 he granted the town to his youngest son Mieszko, who renounced it in favour of his brother Władysław. In 1337 it was acquired by Casimir I, Duke of Cieszyn, whose scion Wenceslaus I sold it to the Archbishop of Kraków in 1443. Zygmunt Gloger in his book "Historical geography of lands of ancient Poland" ("Geografia historyczna ziem dawnej Polski"), published in 1900, writes that the Duchy of Siewierz belonged to Lesser Poland, after it was bought by the Archbishops of Kraków.[1]
Since 1443, after its acquisition by Archbishop Zbigniew Cardinal Oleśnicki for 6,000 silver groats,[2] it was, alongside the Duchy of Nysa, the only ecclesiastical duchy in the region[which?] (ruled by a bishop of the Catholic Church). On many levels this tiny principality was almost a 'country within a country': it had its own laws, treasury and army.
^Zygmunt Gloger Geografia historyczna ziem dawnej Polski "Właściwą Małopolskę stanowiły województwa: Krakowskie, Sandomierskie i Lubelskie, oraz kupione (w wieku XV) przez Zbigniewa Oleśnickiego, biskupa krakowskiego, u książąt śląskich księstwo Siewierskie"