A town on the Płońsk Upland, over Płonka (right tributary of the Wkra river). The center of the processing industry (Hortex plants, grain mill), automotive (Ford assembly plant), printing (Elanders), grocery (confectionery factory – PepsiCo Wedel SA ). Ok. 22900 inhabited. The seat of the commune and commune offices. From 1999 r. county town. The vicinity of Płońsk is famous for the cultivation of fruit bushes – especially raspberries, strawberries and black currants. The Płońsk Cultural Society operates in the city.
Castle mentioned in 1155 r. in the privilege of prince Bolesław Kędzierzawy for the Benedictine abbey in Mogilno. In year 1385 was given to the Teutonic Knights. King Władysław Jagiełło bought it in 1397 r. City rights from approx. 1400 r. from the granting of the Duke of Mazovia, Siemowit IV. Heyday in the 15th and 16th centuries. Then the development of craftsmanship (shoemaking and brewing) and trade (especially horses and cattle). W 1527 r. there was an extension of privileges by the granting of Chełmno rights by king Zygmunt I the Old. From 1656 r., after the devastation of war, district regress. W XVII i XVIII w. Płońsk enjoyed a bad reputation as a place of the so-called. witch hunts and trials of women accused of witchcraft. During the Polish-Russian war 1831 r. near the city, a skirmish of a unit led by Lt.. Paszyca with a unit of Cossacks. During the January Uprising 23-24 January 1863 r. the city was attacked by an insurgent unit under the command of Grotus and disarmed the tsarist infantry rote. W 1867 r. the city was separated from the Płock poviat and a new Płońsk poviat was created. At the end of the 19th century. there was a slight economic recovery (commissioning of a factory of agricultural machines and tools, brewery, brickworks, with oils, vinegar and mead factories) and the development of crafts (shoemaking, cooperage and pottery). At that time, the city had approx. 8000 inhabited. During the Polish-Bolshevik war between Płońsk and Raciąż 14-16 of August 1920 r. there was a Polish fight 18 DP i 8 cavalry brigade with the Bolshevik IV Army. W 1924 r. the Nasielsk-Sierpc railway line was run through Płońsk, which contributed to a slight revival of the city. In early 1939. the city counted close 11000 inhabited. During World War II, it was incorporated into the Third Reich. At the beginning of the German occupation, Jews from Płońsk were sent en masse to the labor camp in Nosarzewo. In May 1940 r. in the city, along ul. Warszawska (ibid. a monument), a ghetto was created for approx. 10000 Jews from Płońsk and the surrounding area. In November and December 1942 r. they have been liquidated, and the Jews were transported to the extermination camp in Treblinka. In January 1945 r. the Nazis murdered just before their escape from the city 73 underground soldiers imprisoned here (monument in the railway area at ul. Płocka). In the post-war period, there was a significant development of industry, the industrial district was located on the road to Bydgoszcz. Jan Walery Jęd-rzejewicz lived and worked in Płońsk (1835-87), doctor and astronomer, author of the textbook "Kosmografia" published in 1886 r. He ran an astronomical and meteorological observatory here. He dealt with comets and the so-called. double stars. He was a pioneer in Poland in the field of astronomical spectroscopy. He is world famous for his astronomy articles published in foreign journals. Another social activist in Płońsk continued his interest in meteorology, running a meteorological station after Jędrzejewicz's death – Leon Rutkowski (1862-1917). He conducted research in the field of anthropology, he collaborated with the Polish Academy of Arts and Sciences and made great contributions to the cooperative movement. Dawid Ben Gurion also came from Płońsk (responsible. David Gruen, 1886-1973) – later Prime Minister of Israel.
Early medieval stronghold called Łysa Góra or Szwedzka Góra, at ul. 19 January, z XI-XIII w., where the prince's stronghold was later built on the hill above Płonka, probably with a wooden lock replaced by approx. 1400 a brick castle destroyed in 1656 r. (the. 19 January).