In antiquity it was called Keria and the first reference to this name dates to 425 BC, on an inscription of the taxpaying allies of the Athenian Republic. According to the inscription, the isle was inhabited during Classical antiquity. During the Middle Ages until the establishment of the new Greek state it was used as a base for pirates.
The ancient city was built at a spot connecting the island with the neighboring islet of Daskalio, nowadays sunken in the sea.
Excavation work carried out on the island’s western side have brought to light finds of exceptional importance, including over 100 marble figurines, among them ancient harpist and flute players, kept at the National Archaeological Museum of Athens, as well as an impressively sized statuette, 1.40m in height, of the Grand Mother deity.
The oldest known archaeological reference is that of U. Kohler (1884), who attributes to a tomb on the island (but without determining the precise location) the two famous figurines kept at the National Archaeological Museum in Athens, of the harpist and of the flute player, together with two female figurines of the common type with folded arms - which we now know to belong to the Protocycladic II period.
One more harpist’s figurine, at the Metropolitan Museum of New York today, is thought to originate in Keros, while the large head of another figurine is exhibited at the Louvre, Paris.
During classical times, the island was known as Keria and was a member of the Athenian Alliance.
In medieval times it served as a base for pirates, while, later on, it was owned by the monastery of Panagia Chozoviotissa of Amorgos.