The island of Kea has been inhabited since the late Neolithic times, known as Hydroussa at that time. However, the history of Kea is mixed with mythology, according to which the vast springs and fountains of this island were home to the nymphs. These nymphs are said to be chased off Kea by a fierce lion sent by the gods, who were jealous of the beauty of this island. To please the lion, the inhabitants carved a lion statue on the rocks and this statue exists till today outside of Ioulida.
According to their plans, after this, the place became dry and started to be ruled by the star Sirius. Then, the displeased inhabitants went for help to the son of Apollo, the semi-god Aristaios and the nymph Kyrini. They built a temple to Zeus, as he was the one who was in charge of sending rain, apart from being the most powerful god. Since he felt pleased by this gesture, he brought the rain, and so the nymphs returned, as well as the beauty of the island.
The first historical fact that the resources point out, apart from the prehistoric settlement that has been found in Agia Irini area, is the Persian invasion and the battles of Salamis and Artemisium. Kea fought against both of them along with Athens and these were the only Cyclades islands to fight on the Greek side, along with Naxos, Tinos, and Kythnos. This is just an example of the historical relationship between Kea and Athens.
The final victory against the Persians came in 479 BC and took place at Plataea, where the 31 fighting states dedicated a trophy to Apollo, who was said to be placed in the sanctuary at Delphi. This is fact was confirmed in 1912 when this trophy (a column) was uncovered in Constantinople. Once it was carefully cleaned, the names of these winning states- among which the proud Kea is found- became intelligible. These were scripted on the bronze serpents decorating the column, on their lower coils.
Kea was also the first of the islands of Cyclades to fight in the War of Independence. In the 20th century, it developed some industry, such as the factory of Enamel, but most of these factories gradually closed and a large part of the inhabitants migrated. A small island between Kea and Attica, Makronissos, served as an exile location for communists during the junta of 1967-74.