Background and Origin
Arganthonios (Argantonio in Spanish) was king the most important king of ancient Tartessia (southern Spain). The name Arganthonios derives from the Etruscan name "arcnti". To the Cempsi (neighboring Celtic tribe in the meseta of Spain) "argan" meant silver. So the name could mean "king of silver" or "man of silver". Tartessia and all of Iberia was rich in silver. There are other Celtic names that form the same term: -eilin (elbow of silver), Argeitlan (hand of silver). Arganthonios seems to have been more of a title than his real name.
According to Herodotus, Arganthonios was rules Tartessia as king for 80 years, from 630 to 550 BC. Much of this Tartessian dynasty is told in legends, so no one knows what of him is actually historical. He is said by the Greeks to have lived for 120 years while other state that he lived a longer 150 years. His empire consisted all of Andalucía and extended to the Cabo de la Nao (a cape east the Costa Blanca, south of the Gulf of Valencia). His empire was what possibly attracted Greek colonists to the Spanish coast. One of those colonies was Mainake, present day Málaga. Though the capital of Tartessia sank in the mouth of the swampy Guadalquivir River (and now is famously thought of to have been Atlantis), its ruins show great fortifications and columns though hard to see as it is under water. Herodotus records his death after a naval battle between the Greeks and a united fleet of Carthaginians and Etruscans. The battle was a Greek victory. But loosing over half of its fleet, the Greeks stopped challenging military dominance in the area and Tartessia, without an ally, became exposed to Carthaginian expansion.
The Greek historian Strabo wrote about the wealth and great generosity of Arganthonios in the story of a Greek sailor called Koliaos whose ship was blown off course and landed in Tartessos. After being royally entertained for some months, his ship was loaded up with silver and he was sent home. The story also tells how Arganthonios gave the Greeks 1 1/2 tons of silver to build defensive walls to protect themselves from the Persians.
Battle of Alalia (?)
A battle with no official name, before the death of Arganthonios, the Greeks and a fleet of Etruscan and Carthaginian ships fought off the coast of Alalia. The Greeks with 90 ships and the Etruscans and Carthaginians with 120. The Greeks won the battle but lost 40 ships and lost dominance in the western Mediterranean.
Alalia is present day Aléria, Corsica.
By 500, Tartessia would have already suffered from Carthaginian attacks. The capital was surrounded and its walls demolished. When the capital fell the city and the empire sank into the Guadalquivir river. Mainake, the Greek colony which protected Tartessia from Carthage, also sank.
The Greeks back at Olympus compared Tartessia to Atlantis and Hesperides and possibly Tartessia was Atlantis. Hearing all these rumours about silver, good life, and luxury, the Greeks named the isolated west Isles of the Blessed, Tartessos.