Ionia was a land that included the coastal districts and islands of western Asia Minor. The name was derived from the Ionians, one of the four most ancient tribes in Greece. According to the usually received tradition, after being driven out of the Peleponnesus, they migrated to Attica, where, about 1060 BC, they sent forth warrior bands to settle on the bays and promontories and islands of Asia Minor; but it is more probable that the immigration was gradual and spread over a long period of time.
Although mountainous, Ionia embraced the three valleys watered by the Hermus, Cayster, and Meander, and was a beautiful and fertile country, extending, according to Ptolemy, from the river Hermus to the river Meander, though Herodotus and Strabo make it somewhat larger. It soon reached a high point of prosperity; agriculture and commerce flourished; colonies were sent out, which settled on the shores of the Black Sea nd in the south of Gaul (Masalia); and great cities arose, of which Ephesus, Smyrna, Clazomenae, Erythrae, Colophon, and Miletus were the most celebrated. These cities, with six others, formed the Ionian League. Each retained its independence, the form of government being democratic; but all met together periodically at Panionium, near Priene, for the discussion of such affairs and interests as they had in common, for religious worship, and for the celebration of athletic games. A few centuries later the twelve cities were made thirteen by the accession of Smyrna. These Ionian states were gradually subdued by the kings of Lydia. Then they passed (557 BC) under the sway of the Persians, but were allowed a considerable measure of internal liberty. They revolted, however, in 500, but were reduced to subjection after a bloody battle near Ephesus in 496 BC.
During the great Persian war the contingent which they furnished to their oriental masters deserted to the Greeks at the battle of Mycale (479 BC); thereupon the Ionians entered into an alliance with Athens, upon which they now became dependent. By the peace of Antalcidas (387 BC) they were again made subject to the persians, and remained so till the time of Alexander the Great. From this period Ionia shared the fate of the neighboring countries, and in 64 BC was added to the Roman empire by Pompey, after the third Mithridatic war.
The Ionians were wealthy and luxurious; and the fine arts were cultivated among them at a much earlier date than among their kinsmen in the mother country. Two of the celebrated temples of the Greek world, that of Diana and that of Apollo, both near Ephesus, were in Ionia.
The Ionian School was the name given to the representative philosophers of the Ionian Greeks, such as Thales, Anaximander, Anaximenes, Herclitus, and Anaxagoras, who devoted themselves mainly to the question what was the primordial constitutive principle of the universe.
The Ionian dialect, nearly akin to Attic, excels the other Greek dialects in softness and smoothness, chiefly from the greater richness of its vowel system.