Paros was taken by the Samians in the 6th century BC, a period in which the great natural philosopher Pherecydes pupil of Pittacus, who became a teacher of Pythagoras, when he was in Samos, was born. The local tradition, actually shows on the eastern side of the island where the cave in which the philosopher is said to have lived. There is another site that is linked to Pherekydes in the location Alithini between Ermoupolis and Ano Syros.
During the Persian wars, Syros was conquered by the Persians, but in 478 BC it was part of the Delian League paying taxes to the Athenians. He maintained, however, the autonomy of having its own parliament and senate. In the island as evidenced by the coins found, Asfalios Poseidon, Amphitrite, Athena, Pan, Demeter and Persephone, the Cabiri, Dionysus, Hermes, Apollo and Hercules were worshiped.
Syros was subjugated to the Macedonians in 338 BC, after the battle of Chaeronea, and it seems that it has maintained its regime even after its conquest by the Romans. During the 3rd and 2nd century BC, the circulation of copper and silver coins testifies its growth. In the Byzantine period it followed the fate of the other Cyclades, in the 7thcentury it suffered from Arab raids and from 747 to 750 it was severely tested by famine.
After the Capture of Constantinople in 1204 by Frankish Crusaders, Syros belongs to the Venetian Duchy of Naxos under Marco Sanudo (1207). In1284 it was given from Marco II Sanudo to his eldest son William so as to become a fief of his successors for a century. In 1383 the Duke of Naxos Francesco Crispo gave Syros as fief to Peter Andrea Zeno, who had married his daughter Petronella. During the first quarter of the 15th century, the island lived in terror and faced extreme poverty with residents as reported by sources being fed on locust beans. It was the period in which master of the island was Nicholas Crispo. In 1494 Venice took command and sent a Venetian rector there.
The Ottomans occupied Syros in the mid 16th century, and from 1566 to 1579 they gave it to the Jewish banker Joseph Nasi. At that time, the population raised to 3,000 people. After the death of Nazis and until 1582 Syros with Andros, Naxos, Paros and Santorini were given to Suleiman Bey in place of taxes. In 1580 the Sultan, at the request of the Syrians and residents of other Cycladic islands, ceded the island administrative, ecclesiastical, and judicial and tax privileges. As mentioned in sources, it was not under the dominance of Kapudan Pasha (Admiral) of the Ottoman fleet, but under the governing of Ottoman Constantinople magnates.
Piracy tormented the island from the late Venetian period throughout the period of the Ottoman rule and until the 18th century. Important event in local history was the raid Ali Tselepi Kapudan Pasha in 1617. On the pretext of the negative attitude of the Catholic population against the Turks, he killed the Roman Catholic bishop Andreas Kargas and some elders; he kidnapped 300 Syrians and destroyed the city burning mills and houses.
Regarding the population, most people followed the Roman Catholic doctrine, keeping, however, the Greek language. When in 1700 the famous traveller and botanist Tournefort visited the island, it had the bigger number of Catholics in the Aegean Sea. He notes that there were only 7-8 Orthodox families in Syros, with the Catholics being 6000. However, the travellers and the sources of the 17th century mention the existence of Orthodox churches, such as those of St. Nicholas the “poor”, the Virgin Mary Faneromeni, Agia Triada, Agia Paraskevi. In 1635 Capuchin monks settled on the island who worked in education. The next century Jesuits and nuns of the Order of Ursulines came to the island.
At the time of the Orloff movement (1770-1774) Syros was captured the Russian fleet. In those years, there are references to the names of Giannoulakis Salachas, Demetrios Douratsou and Giuseppe Rossi as a local “Syndiki” (administrators). In 1774, after the Treaty of Küçük Kaynarca, the Sultan Abdul Hamid beheaded the Bey of Syros and afterwards ceded the island to his beloved niece Shah Sultana, sister of Sultan Selim who later succeeded him.
After the capitulation between the French and the Ottomans, the Catholic population of Syros enjoyed the protection of France. This privileged status was maintained until the time of the Revolution of 1821, a period during which the island kept its neutrality. This fact led to the economic progress of the Syrians from the late 18th to the 19th century, making the port a major shipping centre. During the Revolution, sailors and merchants from Chios, Psara and Kassos fled here as refugees, gradually changing the proportion of Catholic and Orthodox population.
From the time of the Struggle, Syros became an administrative and cultural centre. At the port they traded wheat and ammunition, and the sale of the spoils of war and piracy was going on. In 1828 the inhabitants of the island reached in number 13800, thanks to the gradual arrival of refugees from the islands of the eastern Aegean, Smyrna and Kydonies.
Until 1860, Syros was the first commercial port of the newly established Greek Kingdom, in terms of traffic. It was an international logistics centre between Europe and the East. Textile, silk, leather and iron trade was flourishing. The existence of a banking and credit system reinforced the shipping, trade,crafts,culture. The decline of the port of Syros is connected to the end of the sailing boats and the development of steam shipping. Then came the turn of Piraeus to become the first commercial port in the country.