Fast Facts on the Greek Colonies > Ionia
Who the Ionians were and whence they came to Greece is not entirely certain. Solon, Herodotus, and Homer (as well as Pherecydes) believed they originated on the mainland in central Greece. The Athenians considered themselves Ionian, though the Attic dialect is somewhat different from that of the cities of Asia Minor. Tisamenus, grandson of Agamemnon, evicted from the Argolid by Dorians, drove the Ionians from the Northern Peloponnese into Attica, after which time that district was known as Achaea. More Ionian refugees arrived in Attica when the Heracleidai drove Nestor's descendants from Pylos. The Neleid Melanthus became king of Athens, as did his son Codrus. (And hostilities between Athens and Boiotia date back at least to 1170 B.C. if we accept Thucydides' dates.)
Neleus, son of Codrus, was one of the leaders of the Ionian migration to Asia Minor, and was thought to have founded (re-founded) Miletus. Along the way his followers and sons occupied Naxos and Mykonos, driving the Carians out of the Cycladic islands. Neleus' brother Androclus, known to Pherecydes as the instigator of the migration, drove the Lelegians and the Lydians out of Ephesus and founded the archaic city and the cult of Artemis. He found himself at odds with Leogrus of Epidaurus, king of Samos. Aepetus, one of the sons of Neleus, founded Priene, which had a strong Boeotian element in its population. And so on for each city. Not all were settled by Ionians from Attica: some settlements were Pylian, some from Euboea.
The above is from the notes of Sallie Goetsch of Didaskalia.
Primary Sources and Select Passages:
Strabo 14.1.7 - Milesians.
Herodotus Histories Book I:
Herodotus Histories Book I.56. By these lines when they came to him Crœsus was pleased more than by all the rest, for he supposed that a mule would never be ruler of the Medes instead of a man, and accordingly that he himself and his heirs would never cease from their rule. Then after this he gave thought to inquire which people of the Hellenes he should esteem the most powerful and gain over to himself as friends. And inquiring he found that the Lacedemonians and the Athenians had the pre-eminence, the first of the Dorian and the others of the Ionian race. For these were the most eminent races in ancient time, the second being a Pelasgian and the first a Hellenic race: and the one never migrated from its place in any direction, while the other was very exceedingly given to wanderings; for in the reign of Deucalion this race dwelt in Pthiotis, and in the time of Doros the son of Hellen in the land lying below Ossa and Olympos, which is called Histiaiotis; and when it was driven from Histiaiotis by the sons of Cadmos, it dwelt in Pindos and was called Makednian; and thence it moved afterwards to Dryopis, and from Dryopis it came finally to Peloponnesus, and began to be called Dorian.