Question: Why was Boreas the son-in-law of the Athenians?

Answer:

Boreas is the name of the god of the north wind. He had a special relationship with Athens during the Persian Wars. Advised by the Delphic Oracle to call on their son-in-law to help them against the fleet of the Persian king Xerxes, the Athenians interpreted this to mean Boreas. Summoned, Boreas or the north wind destroyed Persian ships, and so Boreas was ever afterward honored with an annual festival.

Boreas was a son of Astraios and Eos (Dawn). He was the son-in-law of Athens because after he had abducted Oreithuia (Oreithyia), a daughter of the Serpent-bodied king of Athens, Erichthonius (Erechthonius), and took her to his homeland Thrace, Boreas made her his wife.

More on Boreas

Aeschylus and Sophocles wrote plays about Oreithuia. Many 5th century vases tell the story of the son-in-law relationship between the Athenians and Boreas. Boreas is sometimes shown as a middle-aged man with a beard and wings. One representation shows him with a pair of heads like Janus. Sometimes he is wreathed. The Oreithuia painter depicted Boreas with icicles for hair.

Boreas and Horses

Boreas, like Poseidon, sometimes appeared in horse form. Homer (Il. 20.220) says that in this way, Boreas mated with the 3000 mares owned by Erichthonius, the son of Dardanos (in the area where Troy would soon be), siring 12 colts.

Ancient Sources on Boreas:

• Herodotus 7

  189. There is a story reported that the Athenians had called upon Boreas to aid them, by suggestion of an oracle, because there had come to them another utterance of the god bidding them call upon their brother by marriage to be their helper. Now according to the story of the Hellenes Boreas has a wife who is of Attica, Oreithuia the daughter of Erechththeus. By reason of this affinity, I say, the Athenians, according to the tale which has gone abroad, conjectured that their "brother by marriage" was Boreas, and when they perceived the wind rising, as they lay with their ships at Chalkis in Euboea, or even before that, they offered sacrifices and called upon Boreas and Oreithuia to assist them and to destroy the ships of the Barbarians, as they had done before round about mount Athos. Whether it was for this reason that the wind Boreas fell upon the Barbarians while they lay at anchor, I am not able to say; but however that may be, the Athenians report that Boreas had come to their help in former times, and that at this time he accomplished those things for them of which I speak; and when they had returned home they set up a temple dedicated to Boreas by the river Ilissos.

• Strabo

  ... (I)n fact, if even Sophocles, when in his role as a tragic poet he speaks of Oreithyia, tells how she was snatched up by "Boreas" and carried "over the whole sea to the ends of the earth and to the sources of night and to the unfoldings of heaven and to the ancient garden of Phoebus," his story can have no bearing on the present inquiry, but should be disregarded, just as it is disregarded by Socrates in the Phaedrus. But let us confine our narrative to what we have learned from history, both ancient and modern.

• Plato, Phaedrus 229

  Phaidros: I should like to know, Sokrates, whether the place is not somewhere here at which Boreas is said to have carried off Oreithyia from the banks of the Ilissos? .... Sokrates: Oreithyia was playing with Pharmakeia, when a northern gust carried her over the neighbouring rocks; and this being the manner of her death, she was said to have been carried away by Boreas.

Sources:

• "Boreas at Athens," Walter R. Agard The Classical Journal, Vol. 61, No. 6. (Mar., 1966), pp. 241-246.
• Early Greek Myth, Timothy Gantz. Johns Hopkins University Press: 1993.