Ciechanów AUDPl-Ciechanów.ogg t͡ɕeˈxanuf is a city in north-central Poland. From 1975 to 1998, it was the capital of the Ciechanów Voivodeship. Since 1999, it has been situated in the Masovian Voivodeship. As of December 2021, it has a population of 43,495.
The settlement is first mentioned in a 1065 document by Bolesław II the Bold handing the land over to the church. The medieval gord in Ciechanów numbered approximately 3,000 armed men, and together with the region of Mazovia, it became part of the emerging Polish state in the late 10th century.
In 1254, Ciechanów is mentioned as the seat of a castellany (Rethiborius Castellanus de Techanow (Racibor, Kasztelan Ciechanowa)). In 1400 Janusz I of Czersk granted Ciechanów town privileges. The area eventually become a separate duchy with Casimir I of Warsaw using the title "dominus et heres lub dominus et princeps Ciechanoviensis." In the Middle Ages, the defensive gord of Ciechanów protected northern Mazovia from raids of Lithuanians, Yotvingians, Old Prussians and later, the Teutonic Knights. It is not known when it was granted a town charter. This must have happened before 1475, as a document from that year, issued by Duke Janusz II of Warsaw, states that Ciechanów has a Chełmno town charter.
In the period between the 14th and 16th centuries, Ciechanów prospered with the population reaching 5,000. In the late 14th century, Siemowit III, Duke of Masovia, began construction of a castle, while his son Janusz I of Warsaw invited the Augustinians, who in the mid-15th century began construction of a church and an abbey. The Augustinian Friars were brought to Ciechanów in 1358 by Duke Siemowit III. They experienced the most turbulent times during the Reformation. From the 17th century, the Augustinians’ pastoral presence was growing in the towns. The monastery – characterised by mild observance – was usually inhabited by 4 to 7 monks. It ceased to exist in 1864 when monasteries were dissolved.
In 1526, together with all Mazovia, Ciechanów was incorporated to the Kingdom of Poland.