The island's Peloritani, Nebrodi, and Le Madonie mountain chains are structurally a continuation of the Apennines. The highest elevation is atop Mount Etna. Approximately 25% of the working population  are engaged in agriculture, growing wheat, citrus fruits, vegetables, olives, and grapes for wine. Retailing, service, and civil service occupations account for about half the island's income. Sicily's industries produce refined petroleum, ships, chemicals, pharmaceuticals, processed foods, fertilizers, sulfur, and other minerals. The island's three main ports are Catania, Messina, and Palermo. Tuna and other fishing dominate the coastal economy.

Sicily, the largest and most populous island in the Mediterranean, has been settled and ruled by many peoples. Its earliest-known inhabitants were the Elymi, Sicani, and Siculi. From the 8th century BC Phoenicians, Carthaginians, and Greeks established settlements on the island. In the 5th century BC the leading Greek city, Syracuse, established hegemony over the other Greek colonies (including Agrigento, Gela, Catania, Himera, and Messina). It faced a vigorous challenge from the Carthaginians, however, who by the end of that century controlled half the island. In the mid-3d century the Romans intervened against the Carthaginians on Sicily, precipitating the First Punic War (264241 BC). After the Roman victory and the death of Hiero II of Syracuse, Rome gained control of most of the island, and Sicily became known as the Breadbasket of Rome.

Sicily was taken by the Vandals and then the Goths in the 5th century AD. In 532 it came under Byzantine rule, and in the 9th century it fell to the Muslim Arabs. The Arabs, who promoted both economic and cultural development, were driven out by the Normans in the late 11th century. The Norman Roger II was recognized (1139) by Pope Innocent II as king of Sicily and of the Norman territories in southern Italy (see Naples, Kingdom of). Through the marriage of Constance, heiress of the last Norman king, to Holy Roman Emperor Henry VI, Sicily passed in 1194 to the Hohenstaufen dynasty. Their son, Holy Roman Emperor Frederick II, spent much of his time in Sicily, where, like Roger II, he effected important administrative reforms. After his death (1250), however, his weak successors were outmaneuvered by the papacy, which placed (1266) the Angevin Charles I on the throne as a papal vassal. Charles's oppressive rule provoked the Sicilian Vespers (1282), a revolt in which the Sicilians chose Peter III of Aragon as their king. Although the Aragonese secured control of Sicily, the Angevins retained Naples, and wars between the two continued until 1373.

The Aragonese allowed Sicily considerable local autonomy, but this policy was reversed after the unification of Spain and the accession to the Spanish throne of the Habsburg dynasty (early 16th century). Sicily passed briefly to the house of Savoy (1713) and then to the Austrian Habsburgs (1720), but in 1734, during the War of the Polish Succession, both Sicily and Naples were conquered by the Spanish Bourbon prince Charles.

When Charles succeeded (1759) to the Spanish throne (as Charles III), Sicily and Naples passed to his son Ferdinand. The Bourbons ruled from Naples until the French forced Ferdinand to flee to Sicily in 1806. After the Napoleonic Wars, Ferdinand formally combined (1816) his realms as the Kingdom of the Two Sicilies. In 1860, Giuseppe Garibaldi took Sicily, which then joined the Kingdom of Sardinia and ultimately became part of united Italy.

During World War II, Sicily was the scene of heavy fighting when the Allies launched an invasion from North African bases on July 910, 1943. Sicily was the birthplace of the Mafia, organizations of brigands that developed in the lawless conditions fostered by centuries of unpopular foreign rule.