Ilia has a very rich history. The largest part of it was taken over in the Archaic Period by the so called Epeioi, descendants of the Achaeans, who migrated to Ilida in 1500BC. It is believe that the area was named after the King Ilios, son of Amfimachos and Yrmina. The most famous Kings of Ilia were Aethlios, Endymionas, Epeios, Aitolos and Ifitos.

Α Ifitos, according to Pafsania, returned the Olympic Games to Olympia. In relation to the Olympic Games, two of the first Olympic champions, Koroivos and Symachos came from Ilia. Trying to control the Olympic Games, the people of Ilida fought against the Pisates who they subdued in 588 BC.

Since then all judges were from Ilia as were the permanent coordinators of the Games. It is known that the people of Ilia took place in the Persian wars while during the Peloponnessian (431-404 BC) and the Korinthian war (395-387BC) they formed a coalition with the Spartans. In the Macedonian Era the Ilians were forced by Philip II (359-336BC) to accept an oligarchic Macedonian government.

Shortly afterwards, in 146BC, the Roman general Lefkius Mommius conquered Ilia making it part of the Roman Empire. In Nero’s time (54-68BC) Ilia had partial independence. In 393AD Emperor Theodosios the Great abolished the Olympic Games as, in his opinion, they were a "pagan residue".

Between 746-783AD the Slavs settled in Ilia who were raiding the Arabes at the time(881AD) followed by the Bulgarians (978AD), the Venetians (1125AD) and the Normans (1150AD). They were all beaten though and forced to leave Peloponnesus. Only the Turks were able to keep Ilia until 1687.

During the Venetian occupation (1687-1715) Ilia suffered much destruction and the people underwent immense religious pressures. In 1715 the Turks re-conquered Peloponnesus which resulted in a cruel and painful occupation. Ilia took part in the Revolution of 1812 and produced many fine leaders (Vilaetis, Moschoulas, Mitsopoulos etc). Ilia was finally free in 1828. In its more recent past Ilia was under Italian occupation (1941-1943) followed by the Germans for a year.