Ancient Motyca stood here, one of the more important prehistoric and classical sites of Sicily, within the domains of the Syracusan tyrant Gelon in the fifth century BC and later under Rome. The Arabs took it in 844–45 and made it a significant agricultural and commercial centre. Under the Normans it was raised to a county — Gualtieri, a captain in Roger's service, was designated Count of Modica — and Roger d'Hauteville introduced the cult of San Giorgio , which the town has kept ever since.

The decisive date is 1296 , when Frederick II of Aragon granted Manfredi Chiaramonte the diploma of the county, naming him Count of Modica and lord of Ragusa, Caccamo, Scicli, Gulfi, Pozzallo and Spaccaforno. From then the Contea di Modica was effectively a state within the kingdom: in practice the Count of Modica ranked with the Viceroy. Its territory covered approximately the modern province of Ragusa, together with the baronies of Alcamo and Calatafimi in the Trapani area and other scattered towns.

Its lords ran through the Mosca, the Chiaramonte , the Catalan Cabrera and the Henriquez-Cabrera , who held it to 1702 ; the county was taken into the royal fisc in 1704 and later reinvested. Under the Henriquez, who lived permanently in Spain, the county was held chiefly to be exploited, and the chancery at Modica dealt with Palermo through an intermediary.

One episode belongs in any honest account of this town. On 15 August 1474 , during the Cabrera period, some 360 Jews were killed at Modica — the best-known and most terrible episode in the history of Sicilian Jewry. If your family tradition here includes a converted or hidden Jewish ancestry, this is the event that context sits against.

The town was damaged by an earthquake in 1613 and then struck by the Val di Noto earthquake of 11 January 1693 , which killed around 3,400 of its roughly 18,000 inhabitants. Unlike Noto, Modica was rebuilt on the same site : the existing urban fabric was partly restructured, especially along the axis of what is now viale Regina Margherita in the upper town and along Corso Umberto below, where the agricultural nobility raised their new Baroque houses. Many of the religious orders that had settled here in the seventeenth century drove the reconstruction.

The county ceased to exist as a political and institutional entity in 1816 , when the Bourbons abolished feudalism, and Modica stopped being a capital.

Water is the other constant. The gorges below the town carried torrents that repeatedly flooded it through the nineteenth century, and after the disastrous 1902 flood the channels were finally covered over. In the cloister of the Palazzo di Città — the former convent of San Domenico — a plaque on one of the columns marks the level the water reached.