The settlement of the Crissaean Field was the core for the development of the later Crisso. This development started gradually during the 6th and 7th centuries AD with the migration of people from the Delphi towards the safer slopes of the Crissaean Field to protect themselves from the Arab and Slavic raids and sustain themselves through cultivating the valley, following a long lasting epidemic that hit men and animals (as attested by the historians Procopius and Evagrios, the patriarch Syrros, the chronicler Theofanis).
It is also likely that this migration was also caused by destructive tidal bores following a series of deadly earthquakes during the 6th century.
The oldest detailed information about Chrisso date back to the Byzantine times. In 1159 a Spanish-Jewish traveller attests the presence of 200 Jewish people owning acres in the area. Towards the end of the 12th century there was a School in Chrisso, where the scholar and churchman Leon Makros studied. In 1147 the area was pillaged by Normans during the Crusades. In 1319 the area was owned by the Catalans, while in 1394, sultan Bayezid II invaded the area. During the long Ottoman occupation Chrisso was the birthplace of many uprisings. Later on, the French ambassador Beaujour Phelix reported that during the decade of 1787-1797, Chrisso was producing a type of dye, extracted from acorns. Chrisso back then could be characterised as a small town, consisting of 180 houses, having its own Episcopal See.
