The borough at the foot of the castle gradually transformed into an early medieval town, coming under German Law of Lwówek Śląski in the 13th century. After the autonomous Duchy of Cieszyn was founded around 1290 the town continued to grow, with its centre being located in the region of the present Plac Teatralny. Cieszyn’s status was assured in 1374 when it received Magdeburg Law and later in 1416 when the Cieszyn Prince, Bolko I, gave the burghers numerous privileges. Cieszyn’s historical centre was finally established at the end of the 15th century, which coincided with a period of great prosperity. In the 16th century there were almost 2,000 inhabitants living in 262 houses in Cieszyn and its outskirts.
       Midway through the 16th century Prince Wacław III Adam established Lutheranism as the dominant religion in the Cieszyn Duchy, and the majority of the townspeople followed him. His son and successor Prince Adam Wacław converted to Catholicism, but the last representatives of the Piast dynasty did not, however, interfere excessively in converting their Cieszyn subjects to the Catholic faith. The Thirty Years’ War, waged in the first half of the 17th century ravaged their lands. Cieszyn did not escape the destruction, being occupied by the Swedish Army in 1645. The Piast era in Cieszyn’s history came to an end in 1653 with the death of Princess Elizabeth Lucretia.