Ionian Islands (Īōˈnēən) [key], chain of islands (1991 pop. 193,734), c.890 sq mi (2,310 sq km), W Greece, in the Ionian Sea, along the coasts of Epirus and the Peloponnesus. The group is made up of Kérkira, Paxoí, Lefkás, Kefallinía, Itháki, Zákinthos, Kíthira, and numerous islets. Largely mountainous, the islands reach their highest point at Mt. Ainos (c.5,340 ft/1,630 m) on Kefallinía. Fruits, grains, timber, olives, wine, and cotton are produced, and sheep, goats, and hogs are raised. Industries include fishing, shipping, and tourism. The islands had no unified history until the 10th cent. A.D., when they were made a province of the Byzantine Empire. Venice took the islands in the 14th and 15th cent. and held them until 1797, when the Treaty of Campo Formio, which ended the Venetian republic, gave the islands to France. In 1799 they were seized by a Russo-Turkish fleet and were constituted a republic under Russian protection. In 1807, by the Treaty of Tilsit, Russia returned the islands to France. From 1809 to 1814 the British navy occupied all the islands except Kérkira. In 1815 the Ionian Islands, known as the "United States of the Ionian Islands," were placed under British protection. The British ceded the islands to Greece in 1864 after considerable popular agitation on the islands. A series of earthquakes in 1953 caused extensive damage.