Duchy of Czersk

The Duchy of Czersk was a feudal district duchy in Masovia, centered on the Czersk Land. Its capital was Czersk.

The country was established in 1275, in the partition of the Duchy of Masovia, with duke Konrad II becoming its ruler. After his death,the duchy was unified with the Duchy of Płock, forming the Duchy of Masovia, on 24 June 1294. The state was again reestablished in 1310, with Trojden I, as its first ruler. It existed until 5 November 1370, when, under the rule of duke Siemowit III, duchies of Czersk, Rawa, and Warsaw were unified into the Duchy of Masovia. It was once again reestablished in 1471, from the part of the territories of the duchies of Płock and Warsaw. In 1488, it incorporated the Duchy of Warsaw, into its territory. It existed until 1495, when, with the incorporation of the Duchy of Płock into the Kingdom of Poland, it remained the only state in Masovia, and subsequently, got reformed into the Duchy of Masovia.

Between 1275 and 1294, it was an independent state, while from 1310 to 1320, it was a fiefdom within the Kingdom of Poland, and from 1320 to 1370 a fiefdom of the United Kingdom of Poland, and from 1471 to 1495, a fiefdom of the Crown of the Kingdom of Poland.

First state

 * Konrad II of Masovia (1275–1294)

Second state

 * Trojden I (1310–1341)
 * Siemowit III and Casimir I of Warsaw (1341–1349)
 * Casimir I of Warsaw (1349–1355)
 * Siemowit III (1355–1370)

Third state

 * Konrad III Rudy (1471–1495)