Following an archaeological research, the presence of the food-collector, palaeolithic man has been established in the area of Achaia, in two neighboring locations at the feet of mountain Movri, near Elaiochorio of the present Municipality of Dymi, where blades and other Paleolithic tools have been found.
The ancient traveler and writer Paphsanias, who visited Achaia in 174 b.c., informs us: "Currently, the land between Helia and Sikyonia along the bay that extends eastward is called Achaia, because it is inhabited by the people of Achaioi, while in earlier years it was called Aigialos and those who possessed it were called Aigialeis after the king of Sikyonia, as it stands today, Aigialeas."
According to excavation findings, it seems that during the Archaic Age (7th – 6th centuries b.c.) Achaia declined, probably because it was confined to its own boundaries, and it was thus isolated from the Pan-Hellenic events.
At the end of the Hellenic-Persian wars (479 b.c.), the shaping of two political-military centers in Greece started: the Athenian Principality and the Peloponnesian Alliance. The Achaioi were again absent from the coming-together of the Greeks and the separation tendencies of Greece, being busy with domestic affairs and, in particular, with financial issues.
The destructive incursions of the Gauls aggravated this financial predicament but they also weakened the declining military power of the Macedonians, something that the Achaioi were the first to realize, in particular the citizens of Patras.
Following the domination of reformer Kleomenes in Sparta, the old hatred of Dorean Lakedemonioi was rekindled and became even greater due to the spectacular expansion of the "Second Achaic Confederation". That resulted in the encouragement of the Aitoloi who had been waiting for the right moment to take action against the Achaioi. As a consequence, there was a first conflict with the "Aitoliki Confederation" (240 – 229 b.c) followed by the so-called "Kleomenean War" (229 – 222 b.c.) and then by the "Allies War" (220 – 217 b.c.).
In multinational Patras of the Roman Age, Protokletos Apostle Andreas taught the Christian doctrine for the first time, in Nero’s reign.
The miracles that Apostolos performed and, in particular, his teachings at the temple of goddess Demetra where his renowned church is now situated triggered the interest of the people of Patras who gathered around him in great numbers.
During the first Byzantine perio, the development of Achaia was hindered due to the invasion of the Goths (395 b.c.), the religious conflict between the Christians and the nationalists, and the great earthquake in 551A.D that shook many areas of the Empire.
Towards the end of the 6th century A.D. Achaia reemerged in the development scene as a result of silk production that helped the economy and spread to other Byzantine regions. However, because the production was so much greater in Achaia and the whole of the Peloponnese, it was renamed into Morias or Moreas, a name that comes from the greek word "mouries" i.e. mulberry trees which were used in the reproduction of silkworms.
The fall of Konstantinoupolis in 1204 was similar to what happened to the rest of Greece as well as to Achaia which was conquered by Goulielm Sablittes on account of the conqueror of
Thessaloniki, Vonifatios Momferattos.
First they conquered Aigio then Patras and then Lower Achaia. Then, Achaia was divided into 48 feuds, 28 of which belonged to the Baron hood of Patras, 12 to the Baron hood of Kalavryta and 8 became the Baron hood of Vostitsa (of Aigio).
The Byzantine domination in the Peloponnese offered a lot to the Italian Renaissance (Plithon Gemistos – Vissarion) but it was only a break in the slavery that lasted so many years, that is from 1430 to 1460, when the Othman Turks conquered Achaia under the rule of Mohamed Porthitis the Second.
When Aigio and the Northwestern Peloponnese tried to recover from the earthquake of 1817, the representative of Filiki Etaireia, Antonios Pelopidas, arrived in Patras from Constantinoupolis, aiming at the conversion of distinguished people of Achaia to the principles of the organization.
