Assos has always had a small population. Its location meant that under siege its supplies, including water, could be cut off. Still, the castle became the capital of northern Cephalonia as a large fort with a small settlement inside. In 1684, the Venetians took Lefkas from the Turks and the Assos castle lost its strategic importance. In 1757, with piracy and the Turkish threat reduced, the Venetians founded Argostoli, which became the main town of the island. Asos remained the seat of the Venetian "provveditore" until the Fall of the Republic of Venice and the end of Venetian rule in Cephalonia. In 1822, about 1700 people came from Souli to stay in the Assos fortress and the whole area became a quarantine area, resulting in a settlement within the fortress named Souli. For the next century, Assos continued to be a fortress without a military role. In the late 1920s, a prison was started there which after the World War II hosted political prisoners, who kept vineyards and crops of cereal. The Ionian Islands were badly damaged by the Ionian Earthquake in 1953. After that, most people of the castle left and the prison was closed. The 1961 census found only 6 people living in the fortress, the last of whom left in 1963. They had been known as the "Kastrinoi" ("people of the castle"), comprising large families who mainly cultivated olives and grapes.