Czersk, Masovian Voivodeship in the context of "Warka"

Bolesław II of Masovia or Bolesław II of Płock (pl: Bolesław II mazowiecki (płocki); ca. 1253/58 – 20 April 1313), was a Polish prince, member of the House of Piast, Duke of Masovia during 1262-1275 jointly with his brother, after 1275 sole ruler over Płock, after 1294 ruler over all Masovia and Duke of Kraków and Sandomierz during 1288-1289. In 1310 he gave to his sons the districts of Warsaw and Czersk. Also High duke of Poland twice (1288, 1289).

The Duchy of Masovia was a district principality and a fiefdom of the Kingdom of Poland, existing during the Middle Ages. The state was centered in Mazovia in the northeastern Kingdom of Poland, and during its existence, its capital was located in the Płock, Czersk and Warsaw. It was formed in 1138 from the territories of the Kingdom of Poland, following its fragmentation, that was started by the testament of Bolesław III Wrymouth. The country existed in the years: 1138–1275, 1294–1310, 1370–1381, and 1495–1526, between that time, going through fragmentations of its territory into smaller duchies and its unification. The states formed during its fragmentation were duchies of Kuyavia, Dobrzyń, Czersk, Płock, Warsaw, Rawa and Belz. In 1526, the country was incorporated into the Kingdom of Poland.

Bolesław the Pious (1224/27 – 14 April 1279) was a Duke of Greater Poland during 1239–1247 (according to some historians during 1239–1241, sole Duke of Ujście), Duke of Kalisz during 1247–1249, Duke of Gniezno during 1249–1250, Duke of Gniezno-Kalisz during 1253–1257, Duke of the whole of Greater Poland and Poznań during 1257–1273, in 1261 ruler over Ląd, regent of the Duchies of Mazovia, Płock and Czersk during 1262–1264, ruler over Bydgoszcz during 1268–1273, Duke of Inowrocław during 1271–1273, and Duke of Gniezno-Kalisz from 1273 until his death.

He was the second son of Władysław Odonic, Duke of Greater Poland by his wife Jadwiga, who was probably the daughter of Mestwin I, Duke of Pomerania, or a member of the Přemyslid dynasty. His name was very popular in the Piast dynasty, so it is unknown exactly after whom he was named. Very soon Bolesław received the nickname of "the Pious" (Latin: Pius, Polish: Pobożny), given to him during his lifetime by the Chronicle of the Chapter of Poznań. In 1264, Bolesław granted the first written privilege to the Jews of Greater Poland.

Siemowit III of Masovia (alternatively Ziemowit III; c. 1320 – 1381) was a prince of Masovia and a co-regent (with his brother Casimir I of Warsaw) of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia.

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.

Czersk Land (Polish: ziemia czerska, named after the town of Czersk) was an administrative unit (ziemia) of the Kingdom of Poland and the Polish–Lithuanian Commonwealth. With its capital in the town of Czersk, it belonged to the Masovian Voivodeship.

The history of Czersk Land as a separate administrative unit dates back to 1245, when Duke Konrad I of Masovia moved the seat of the castellany from Grójec to Czersk, making Czersk the major urban and political center of southern Mazovia. In 1377, Siemowit III, Duke of Masovia called a council in Sochaczew, during which he disbanded castellanies, and following the example of the Kingdom of Poland, created ten lands, all divided into counties. Therefore, the Land of Czersk was established, with three counties: Czersk, Warka and Grójec. It stretched from Mińsk Mazowiecki to Grojec, along both banks of the Vistula, including the town of Garwolin.