Around the 14th century BC the Minoans settled on the island and after them the Achaeans followed by the Dorians a few centuries later who build the ancient city of Kos. The island has been concurred by the Persians during the 5th century, but after the sea battle of Salamina the Athenians took control of the Island. Around 460 BC in Kos, Hippocrates was born, renowned as the father of modern medicine who moved practices away from the previously supernatural and religious approach, towards a modern approach of observation, classification, causes and effects.
The Spartans invaded Kos in 411 BC but after a short period the island became again an ally with Athens in 394 BC and democracy has been introduced to the inhabitants. During this period there was a great economical, educational and cultural growth.

In 335 BC Kos became a part of the Macedonian Empire. During the wealthy Byzantine period it became target of dangerous pirates like the Saracens. In 1204 AD the island has been occupied by the Venetians and after them in 1315 AD the Knights of Saint John took control and they build the Castle of Neratzia which stands today in the harbor of Kos and also the Castle of Antimachia. From 1522 until 1912 the island was under Turkish domination until the Italians took control and expelled most of them from the island.

A lot of great buildings built during this period are still used today by the local authorities. Most of the island destroyed during the catastrophic earthquake of 1934. For almost two very difficult years the island had been occupied by the Germans from 1943 until 1945, after which it came under the British Empire. In 1948 Kos was reunited with the rest of Greece.