In the mid-14th century, King Casimir III the Great founded here a fortified castle and the "Church of Saint Ladislaus". The town was surrounded by a defensive wall, with three gates—Kraków Gate, Opatów Gate, and Water Gate. Soon afterwards, Szydłów became the seat of a starosta, and first artisans came here, as well as Jewish settlers. The town was located in Lesser Poland's Sandomierz Voivodeship, and its location helped wine, cattle and hops merchants, who would go with their goods to Sandomierz. In the 16th century, Szydłów emerged as a center of cloth-making. Also, tailors, bakers, shoemakers, iron smiths, saddle makers, sword makers and pot makers worked here, there also was a brewery. In 1528, waterworks and bath houses were opened, and in 1564, the town had 180 houses, of which 49 were located on the market square, but next year, large parts of Szydłów burned in a fire. At that time, a number Jews settled in the town, who in 1534–1564 built first synagogue.