Duchy of Wizna

History

Following the death of the ruler of the Duchy of Rawa, Siemowit II of Masovia, on 18 February 1345, Bolesław III of Płock had inherited from him lands of Sochaczew, Gostynin and Wizna. While the first two were incorporated into the Duchy of Płock, the later one was reformed into Duchy of Wizna, remaining in the personal union with Płock. After Bolesław III's death in 1351, on 18 September, the duchy was inherited by the king Casimir III the Great and incorporated into the Kingdom of Poland. In 1370 the territories of the former duchy were transferred to the Duchy of Masovia.

In December 1381, following the death of his father, Siemowit IV had inherited Wizna Land reestablishing the state. On 2 December 1382, he had pledged the lands of the duchy to the State of the Teutonic Order in exchange of 7 000 grzywnas. In November 138 Siemowit IV had longed the period of the pledge in the exchange for 60 000 Prague groschen. In December 1401, he had bought back the Wizna Land from the State of the Teutonic Order which he impliedly pledged to his brother, Janusz I of Warsaw, ruler of the Duchy of Warsaw, for the duration of 9 years. Despite that, Siemowit IV had continued to title himself the Duke of Wizna, while his brother remained from developing the administration and investing in the territory until 1410. The land had remained under Warsaw control until 1435, when it was given to Władysław I of Płock, ruler of the Duchy of Płock and remained in the personal union with the state until 1495 when it was incorporated into the Kingdom of Poland.