The most celebrated story about him is that which forms the subject of the Ion of Euripides. Apollo had visited Creusa in a cave below the Propylaea, and when she gave birth to a son, she exposed him in the same cave. The god, however, had the child conveyed to Delphi, and there had him educated by a priestess. When the boy had grown, and Xuthus and Creusa came to consult the oracle about the means of obtaining an heir, the answer was, that the first human being which Xuthus met on leaving the temple should be his son. Xuthus met Ion, and recognised him as his son; but Creusa, imagining him to be a son of her husband by a former beloved, caused a cup to be presented to the youth, which was filled with the poisonous blood of a dragon. However, her object was discovered, for as Ion, before drinking, poured out a libation to the gods, a pigeon which drank of it died on the spot. Creusa thereupon fled to the altar of the god. Ion dragged her away, and was on the point of killing her, when a priestess interfered, explained the mystery, and showed that Ion was the son of Creusa. Mother and son thus became reconciled, but Xuthus was not let into the secret. The latter, however, was satisfied, for he too received a promise that he should become a father, viz. of Dorus and Achaeus.
The inhabitants of Aegialus, on the northern coast of Peloponnesus, were likewise lonians, and among them another tradition was current. Xuthus, when expelled from Thessaly, went to Aegialus. After his death Ion was on the point of marching against the Aegialeans, when their king Selinus gave him his daughter Helice in marriage. After the death of Selinus, Ion succeeded to the throne, and thus the Aegialeans received the name of lonians, and the town of Helice was built in honour of Ion's wife. (Description of Greece by Pausanias vii; Apollodorus I) Other traditions represent Ion as king of Athens between the reigns of Erechtheus and Cecrops; for it is said that his assistance was called in by the Athenians in their war with the Eleusinians, that he conquered Eumolpus, and then became king of Athens.
He there became the father of four sons, Geleon, Aegicores, Argades, and Hoples, according to whom he divided the Athenians into four classes, which derived their names from his sons. After his death he was buried at Potamus.From Smith's Dictionary of Greek and Roman Biography and Mythology
The power of Athens had been great before; but, now that the tyrants were gone, it became greater than ever. The chief authority was lodged with two persons, Clisthenes, of the family of the Alcmaeonids, who is said to have been the persuader of the Pythoness, and Isagoras, the son of Tisander, who belonged to a noble house, but whose pedigree I am not able to trace further. Howbeit his kinsmen offer sacrifice to the Carian Jupiter. These two men strove together for the mastery; and Clisthenes, finding himself the weaker, called to his aid the common people. Hereupon, instead of the four tribes among which the Athenians had been divided hitherto, Clisthenes made ten tribes, and parcelled out the Athenians among them. He likewise changed the names of the tribes; for whereas they had till now been called after Geleon, Aegicores, Argades, and Hoples, the four sons of Ion, Clisthenes set these names aside, and called his tribes after certain other heroes, all of whom were native, except Ajax. Ajax was associated because, although a foreigner, he was a neighbour and an ally of Athens.
The Athenian nobles were called EUPATRIDAE, the two other classes in the state being the GEOMORI or husbandmen, and DEMIURGI or artisans. This arrangement is ascribed to Theseus; but there was another division of the people of still greater antiquity. As the Dorians were divided into three tribes, so the Ionians were usually distributed into four tribes. The latter division also existed among the Athenians, who were Ionians, and it continued in full vigour down to the great revolution of Clisthenes (B.C. 509). These tribes were distinguished by the names of GELEONTES (or TELEONTES) "cultivators," HOPLETES "warriors," AEGICORES "goat-herds," and ARGADES "artisans." Each tribe contained three Phratriae, each Phratry thirty Gentes, and each Gens thirty heads of families.
From Lives of the Noble Grecians and Romans By Plutarch
The prices which Solon, in his sixteenth table, sets on choice victims, were naturally far greater; yet they, too, are very low in comparison of the present. The Athenians were, from the beginning, great enemies to wolves, their fields being better for pasture than corn. Some affirm their tribes did not take their names from the sons of Ion, but from the different sorts of occupation that they followed; the soldiers were called Hoplitae, the craftsmen Ergades, and, of the remaining two, the farmers Gedeontes, and the shepherds and graziers Aegicores.