Originally, their main settlements were in the area of Płock, Łomża, Wizna, Czersk, Ciechanów, Płońsk, Zakroczym and Grójec.
Duke Siemowit, being ambitious, was very active in politics of the period and thus needed cash to finance his policies so several times he mortgaged some of his domains to the Teutonic Order, including Wizna, Zawkrze and Płońsk.
Siemowit V (also spelled Ziemowit; 1389 – 16 February 1442) was from 1426-1434 a Prince of Masovia in Rawa, Plock, Sochaczew, Gostynin, Płońsk, Wizna and Belz i.e., hereditary vassal Polish, the breakdown in 1434 goes as follows; prince of Rawa, Gostynin and Sochaczew.