Between 1933 and 1938 an archaeological team discovered remains of a fortified settlement in what is now Stare Bielsko (Old Bielsko) district of the city. The settlement was dated to the 12th - 14th centuries. Its dwellers manufactured iron from ore and specialized in smithery. The current center of the town was probably developed as early as the first half of the 13th century. At that time a castle (which still survives today) was built on a hill. The city of Bielsko-Biała was created on 1 January 1951 when the adjacent cities of Bielsko and Biała were unified.