From the various tombs and foundations of villages discovered by the archaeologist Christos Tountas, mainly at coastal areas of the island, it can be surmised that the first inhabitants settled the island during the second half of the third millennium B.C. The first inhabitants of the island were the Pelasgians, followed by the Carians, the Leleges, and then the Phoenicians. According to mythology, these people were cast out by Minos, the king of Crete, who installed his sons as kings of the Cyclades.
From the findings at the Citadel of Agios Andreas, it can be seen that the island had a golden age and was the centre of proto-Cycladic civilization during the third millennium BCE, while according to tradition, after the Trojan War, Ionians colonized Sifnos, led by Alkenor. After the new inhabitants arrived, a new age began, during which, according to Herodotus, the “asty” was founded on the eastern side of the island, where today’s Kastro lies.
Sifnos has been one of the richest islands of the Cyclades, thanks to its gold mines, silver mines, and the development of the ceramic arts. The existence of such wealth can be verified by the research and excavations as well as by the minting of coinage around 600 B.C. and the rebuilding, in 525 B.C. of the well known "Treasury of the Sifnians” in Delphi, an Ionian building with a rich architectural decoration, and particular aesthetic and artistic value. During the same period, one of the three cities on the island, Sifnos, built an agora and a prytaneum of Parian marble.
During the Persian wars, Sifnos took part in the battle of Salamis with one penteconter, and later became a member of the 1st and 2nd Athenian League.
Due to the negative developments in the broader area over the next years, Sifnos gradually lost the wealth of Ancient period, while during the Hellenistic period and in the years that followed the Roman conquest the island lost a lot of its population due to systematic pirate raids, the same with every other island in the Aegean Sea.
Information on Sifnos during the Byzantine period is extremely limited: during the first Byzantine period Sifnos belonged to the Eparchy of Achaia of the Eastern Illyrian and participated in the small Cycladic fleet; while during the mid-Byzantine period, its commercial standing increased. Moreover, during the times of the iconomachy, many spiritual people and clerics found refuge in Sifnos, thus aiding in its spiritual uplifting.
After the 1204 Crusade, Sifnos was integrated into the Duchy of Naxos, founded in 1207 by Markos Sanoudos. In 1269 it was again conquered by the Byzantines, while in 1307 it was claimed by Giannoulis Da Corogna, who declared himself an independent ruler. Da Corogna fortified the island and the town with a stronghold, to stand up to the dukes of Naxos who would claim the island. In 1964 Sifnos came under the power of the Gozzadini family and remained so until 1566, when the Turks conquered the Cyclades and gave command over the island to Joseph Nasi. However, the Gozzadini remained on the island until 1617, subject to the Sultan and with a shadowy jurisdiction.
With the favourable conditions under the rule of the Sultans over the next years, the island saw great economic and spiritual development.
The economy of Sifnos was mostly based on agriculture and animal farming, less on trade, and was significant, as proven by the existence on the island of consulates from France, England, and Holland.
The renowned School of the Holy Sepulchre was founded in Sifnos in 1687, known as “The School of the Archipelagos”, where great teachers, such as Emmanuel Trochanis and Nikolaos Chrisogelos, taught. The school was attended by more than fifty Sifnians that later went on to excel in the hierarchy of the church, assuming prominent positions within it.
At the same time, the conditions in Sifnos permitted the development of the institution of communal government, mainly with the Public’s General Assembly.
Sifnos participated in the revolution of 1821 and in the liberation with an expeditionary force organized by Nikolaos Chrisogelos, active mainly in Peloponnesus.
After the revolution, Sifnos excelled in every area, but mainly in knowledge, with great scientists, writers and scholars (Ioannis Gryparis, Nikolaos Dekavalas, Konstantinos Dialismas, Iakovos Dragatsis, Aristos Kabanis, Apostolos Makrakis, Aristomenis Provelegios, Theodosis Sperantsas, Antonios Zilimon, Georgios Maridakis, and others).
Sifnos was under Italian rule from 1941 to 1944.
During the 19th and the early 20th century, many Sifnians were Members of Parliament, such as Aristomenis Provelegios, Antonios Prezanis, doctor-general Georgios Koulouris, and others, while Konstantinos Provelegios was Minister of Justice, then Finances, and later of the Interior.
The human creations of outstanding aesthetics, which are characterized by moderation and plasticity are integrated harmoniously into the natural beauty of the landscape and make Sifnos one of the most prized islands for its local culture, its architecture and the quality of its population, who always keep the island neat.
In Sifnos there are 13 villages and beaches that are inhabited all year round and most of their buildings follow the tradition. The central villages of the island are designated and protected as “areas of outstanding natural beauty” since 1962.
The basic characteristics of the sifnian architecture are: the white houses, the flat roofs (in order to collect the valuable rainwater in cisterns), the “flaros” (earthen chimney covers on the rooftops), the paved yards and the paths with their white joints, the windmills, the dovecotes, the countless monasteries and country churches and of course the dry walls (forming terraces) all over the island. The dry walls are used to keep the earth and the rainwater in the fields, to separate the properties and they are the result of the hard work of thousands of people for centuries.
The villages of Sifnos are characterized by multiformity. The town planning at the area of Kastro for example (which has been inhabited uninterruptedly from the ancient times until today) is totally different from the town planning of the other villages of the island, since its character is purely defensive. Despite the years that have passed, it still maintains its medieval character unchangeable.
Nowadays, students from the America and from Europe come to admire and to study the Cycladic and bioclimatic architecture in Sifnos.