Like other towns in Leser Poland, Zawichost prospered in the 15th and 16th centuries. At that time, it was located along a merchant route from Kraków to the Grand Duchy of Lithuania, and profited from taxes on goods transported on the Vistula. In 1564 the town had a number of artisans, a town hall and 126 houses. Good times ended during the Deluge. Zawichost was ransacked and destroyed first by the Swedes (1655), and then by the Transilvanians of George II Rákóczi. The invaders burned the castle, which remained in ruins until 1813, when during a flood its walls collapsed into the Vistula. In 1666 Zawichost experienced a great fire and then a plague, in which most residents died. After all these misfortunes, the town never recovered. Furthermore, after the Partitions of Poland Zawichost was located near Russian - Austrian border, which hampered its development.