Classic Era (480 BC - 323 BC)

According to Herodotus, Skiathos played a leading part
during the Persian Wars. Indeed, in 480 BC, the inhabitants
of Skiathos positioned in “Pyrgi” used torches to warn the
Greeks in Euboea that the Persian fleet had left Thessaloniki
and was about to cross the passage between Magnesia and
Skiathos.

In 478, Skiathos became a member of the Delian (or
First Athenian) League. Thus, on the one hand, it gained
independence but on the other it was forced to pay an annual
tax to maintain the league’s fleet. For the payment of this tax, the Athenians split the members of the league in groups according to the amount they had to contribute. Skiathos was part of the Thrace group that had to pay a relatively small amount, which shows that the island was quite poor at the time. During these times, Skiathos, along with other members of the league, was autonomous and ruled democratically: it had a Parliament, an Ecclesia and a ruler. Unfortunately, the league ended up becoming an Athenian hegemony and ruling over all members of the league.
Classic Era (480 BC - 323 BC)

After the end of the Peloponnesian War (404 BC) and the defeat of the Athenians and given that the ruling of the seas was now on Spartan hands, Skiathos submitted to the Spartans and its regime became oligarchical.

With the Peace of Antalcidas or King’s Peace in 386 BC, all the islands except of Lemnos, Imbros and Skyros gain their independence. Thus, Skiathos as well becomes independent but only for a short period of time, since the Spartans came back after a while violating the treaty. They took over Skiathos again along with other islands, in which they placed military guard and established heavy taxation until 378-377 BC. It was then that Skiathos was liberated by an Athenian General and acceded to the Second Athenian League for the next 40 years or so when it flourishes to the point of even issuing their own bronze coins (Hermes’ Head on one side and the Caduceus with the word “CΚΙΑΘΙ” on the other). Later on, the island was used by the Athenians as a naval base of operations against Philip II of Macedon.

During the Hellenistic and Roman Era (338 BC - 330 AD) and due to its geographical position, Skiathos was on the centre of warfare between the opposing forces of Macedonians, Romans and Rhodians. This resulted in the island being repeatedly destroyed and thus one of the poorest Aegean islands, often thought of as a place of exile. Moreover, because of its proximity to Thessaly and its natural port, Skiathos became a pirate hideout along with the rest of the Sporades.

In 338 BC, after the battle of Chaeronea that essentially ended the independence of the city-states of South Greece and brought over the dominance of the Macedonians, Skiathos was taken over by Philip II of Macedon who established an oligarchy and caused a lot of destruction on the island. Nonetheless, Skiathos was left relatively undisturbed until the death of Alexander the Great in 323 BC, when the island changes many hands.