The city of Bielsko-Biała was created on January 1, 1951 when the adjacent cities of Bielsko and Biała were unified. Bielsko, which for centuries belonged to the Duchy of Cieszyn, was founded in 1312. From 1457 the Biała river was the border between Silesia and Little Poland. Silesia belonged to Austria, Little Poland to Poland. In 1723 on the opposite bank of the river the city of Biała came into being. In 1772 Biała was annexed by Austria and included in the crownland of Galicia. In 1918 both cities became part of reborn Poland, though a significant part of the population was ethnic German. During World War II the city was annexed to the Third Reich and its Jewish population sent to Auschwitz. After the liberation of the city by the Red Army in 1945, the ethnic German population was expelled.

source www.bielsko.biala.pl