The oldest known mention of Żerków comes from a document of Duke Bolesław the Pious from 1257, and in a document of Duke and future King of Poland Przemysł II from 1283 it was already referred to as a town. Żerków was a private town of Polish nobility, administratively located in the Pyzdry County in the Kalisz Voivodeship in the Greater Poland Province of the Polish Crown.
The earliest known mention of Żerków is found in a document from Duke Bolesław the Pious in 1257, and by 1283 it had already been recognized as a town in a document by Duke Przemysł II. As a private town, Żerków was part of the nobility's holdings within the Pyzdry County.