Although some historical sources dating back to the end of the twelfth and the beginning of the fourteenth centuries mentioned the name ‘Sassofortino’ without referring to the castle, many historians believe that the town was not established before the fifteenth century. In 1339, the City of Siena attempted to make efforts to populate the area, in agreement with many inhabitants who had once lived in the castle. This attempt was destined to fail, partly due to the terrible epidemic that struck Europe in the mid-fourteenth century. The two sites were consequently considered abandoned around 1430. Perhaps only the town’s regular urban facilities now show traces of this first Sienese plan. Architectural evidence points to the second half of the fourteenth century, when historical sources allow historians to infer that Siena drew up an agreement with a group of men from Imola and Faenza who planned to move into the area.