Płock

Płock was a Piast duchy in Mazovia, centred on the town on the Vistula. In 1337 Duke Bolesław III ruled the lands inherited from his father Wenceslaus.

Bolesław died without heirs in 1351. Siemowit III reunited most of Mazovia and accepted the Polish king's suzerainty. The partition of 1381 gave Płock to Siemowit IV; in 1495 it became a Polish voivodeship. The remaining Masovian Piast line died out in 1526, and the rest of Mazovia joined Poland.