[3][4] King Casimir IV Jagiellon granted Kościan cloths the first industrial trademark in the history of Poland.

On 29–30 December 1918, local Polish scouts stole more than 900 machine guns, rifles and pistols from a German military warehouse and Kościan was liberated.

[8] During the German occupation of Poland (World War II), the Polish population was subject to mass arrests, executions, expulsions, deportations to Nazi concentration camps and confiscation of property.

[3] The Einsatzgruppe VI carried out public executions of Poles in the town on October 2 and October 23, 1939 as part of the Intelligenzaktion, killing 8 and 18 people respectively, including activists, merchants, landowners, the director of the local narrow gauge railway, the chairman of the local branch of the "Sokół" Polish Gymnastic Society, principals of schools from Kościan and the nearby village of Borowo and one student.

[9] In Kościan, the Germans operated a prison for Poles from both the town and the region, many of whom were later transported to the infamous Fort VII in Poznań.

[15] The Polish resistance movement was active, including local units of the Union of Armed Struggle/Home Army, Narodowa Organizacja Bojowa and the Pakt Czterech secret scouting organization.

[17] In October 1941, the Gestapo arrested the founders of the local unit of the Narodowa Organizacja Bojowa, who were then sentenced to death and executed the following year.