Zygmunt Gloger in his monumental book Historical Geography of the Lands of Old Poland gives a detailed description of Płock Voivodeship: "After childless death of Janusz II, Duke of Łomża, Ciechanów, Wizna and Płock, which took place on February 16, 1495, the Duchy of Płock, except for the Land of Wyszogród, was incorporated into the Kingdom of Poland, and turned into a voivodeship (...) In the 16th century, it had the area of 701 square miles, divided into eight small counties: those of Płock, Bielsk, Raciąż, Sierpc, Płońsk, Szrensk, Niedzborz, and Mława.

The three last counties, located between the Wkra river and Prussian border, made the so-called Zawkrze Land (...) The voivodeship had 67 Roman-Catholic parishes, 63 towns and 1,115 villages.

Most densely populated was Bielsk County (...) Local sejmiks for the voivodeship took place at Raciąż, the town located in the middle of the province.

During the reign of King Stanisław II Augustus, the sejmiks were moved to Płock.

Land courts were located in Płock, Bielsk and Sierpc (since 1726, also in Mława)".