The town was first mentioned as Crosno in 1005,[2] when Duke Bolesław I Chrobry of Poland had a fortress built here in the course of his armed conflict with Emperor Henry II and the West Slavic Veleti confederation.

Due to its strategic location as a point of passage across the Oder,[2] it played an important role at the western border of the Polish kingdom with the Holy Roman Empire during the 11th to 13th centuries.

As a result of the fragmentation of Poland, in 1163 Krosno was part of the Duchy of Silesia ruled by Bolesław I the Tall of the Silesian Piasts.

Henry erected a stone castle at Krosno, where he died in 1238 and where his widow, Hedwig of Andechs, took refuge during the 1241 first Mongol invasion of Poland.

As a former part of the Duchy of Głogów it officially remained a lien of the Bohemian kingdom until in 1538 King Ferdinand I of Habsburg, renounced all rights to Crossen in 1538, thereby finalizing the district's belonging to the Neumark region of the Brandenburg margraviate.