The island was part of Strogyli during prehistoric times. As a result of the great earthquake and the eruption of the volcano in 1650 BC. Thirasia was cut off. According to Ptolemy, Thirasia was an important settlement during the period of the Cycladic civilization. In 1397 AD the Duke of Naxos, assigned Thirasia and Ios to his son. In the middle of the 19th century, Thirasia, like Thera, had mines of Theraic land with exports to countries such as Egypt. During work at the Alafouzou mine, remains of an ancient building, clay vessels and human skeletons were discovered, which were dated to the Late Bronze Age. This was also the trigger for the excavations at Akrotiri of Thira. Great discoveries of the Early and Middle Bronze Age have also come to light from the Koimisi area in the southeast of the island.