Płońsk gained city rights from the prince Siemowit IV of Masovia some time between 1399 and 1412. In the early twentieth century, the population of 10,000 was equally divided between Poles and Jews. The Jews lived mostly within the city, whilst the Poles were more scattered and tended to live in the countryside. Many of the Jewish residents of Plonsk immigrated to pre-state Israel for Zionist reasons, spurred on by the idea of building a Jewish homeland. In September 1940, Jews from the town and the surrounding areas were imprisoned in a ghetto in harsh conditions. Some of them suffering a typhus epidemic. In total, 12 000 Jews were prisoners and from October 1942, they were sent to Auschwitz extermination camp. A resident who returned to the city in 1962 found that the major synagogue, three Jewish schools and the Jewish cemetery had been destroyed and demolished.