The island is said to owe its name to Kephalos, the first king of the area during the Paleolithic era. According to the locals, this king founded the four main cities of the island which were Sami, Pahli, Krani and Pronnoi, and named them after his sons. This explains why the island was called Tetrapolis (Four Towns) during this period. Those four cities were autonomous and independent and had their own regimes and coins. Kefalonia participated in the Persian and Peloponnesian Wars on the side of both Athens and Sparta. Kefalonia is also known for the Cyclopean wall.
Philip of Macedonia tried to attack the island in 218 BC. He was defeated thanks to the help of the Athenians. The Romans took the island in 187 BC after months of fighting against the resistance of the island's inhabitants. That time, the ancient acropolis of Sami was destroyed. The Romans used the island as a strategic spot that would have helped them conquer the mainland. They therefore turned Kefalonia into an important naval base. During this period, the island suffered heavily and frequently from invaders and pirate raids. The threat of the pirates continued growing during the Byzantine period (from the 4th century AD); the most dangerous pirates were the North African ones, the Saracens. In the 11th century the island fell under Frankish rule: it was the end of the Byzantine era. Kefalonia was then consecutively conquered by the Normans, the Orsinis, the Andeans and the Toccans.
The first Turkish attack was made by the famous Ahmed Pasha, in 1480; Pasha and his troupes ruled the island for a short period of time and devastated the island when they left. Following the same faith as the rest of the Ionian Islands, Kefalonia came under the domination of the Venetians and the Spanish. The political and military centers of the island during this period were the Fortress of Saint George and the Castle of Assos, which was destroyed by an earthquake in 1757. The capital moved to Argostoli, and is still there today.
During the Venetian domination the atmosphere was quite conflictive because the islandâ€™s society was divided into three classes. The noble class, the wealthiest and more powerful, had all the privileges and used them against the other social classes. The Venetian rule ended in 1797 with the arrival of the French who were warmly welcomed by the islandâ€™s inhabitants as Napoleon promised them to liberate them (and the rest of the Ionian Islands) from the oligarchic system created by the Venetians.
The French publicly burnt the Golden Book where the names and privileges of the nobles were written. The French were later defeated by the allied fleet of the Russians, the Turks and the English. The Ionian State was founded in Constantinople in 1800 and was under the supervision of the Sultan; the nobles of the island regained their privileges . After a huge popular demand, democratic elections were organized in 1802 and a new Constitution was established in 1803. The island fell again under French domination in 1807 but the new Constitution was maintained.
After the Treaty of Paris, in 1809, the Ionian Islands came under the rule of the English and the "United States of
the Ionians IslandsÂť was established. During the English period various important constructions of public interest were effectuated including the Drapanos British Cemetery, the De Bosset bridge in Argostoli, the Lighthouse of Saint Theodori and the impressive Municipal Theatre of Kefalonia. Despite the fact that Kefalonia, like the other Ionian Islands, remained under the English rule and escaped the Turkish yoke, its inhabitants financially helped the Greek Revolution for independence against the Ottomans who were ruling over the rest of Greece. Kefalonia was finally united to the rest of independent Greece in 1864, the same time as the rest of the Ionian Islands.
During World War II, in 1941, the island was occupied by the Italian troops which were allied with the Germans. In 1943, Italy capitulated but its troupes refused to leave from Kefalonia. As a punishment, the German forces killed more than 5000 Italian soldiers, a historic fact described in the famous book "Captain Corelli's Mandolin", written by Louis de Bernieres.
In 1953 a major part of the island was destroyed by a huge earthquake.