Thermae was founded in the 5th century B.C. by the Greeks, as its name imports, as a thermal spa for Selinunte, whose citizens came there to bathe in the sulphurous springs of Mount San Calogero, which rises up behind the town. We have no account of the existence of a town on the site during the period of the independence of Selinunte, though there is little doubt that the thermal waters would always have attracted some population to the spot. Nor even under the Romans did the place attain to anything like the same importance with the northern Thermae; and there is little doubt that Pliny is mistaken in assigning the rank of a colonia to the southern instead of the northern town of the name. Strabo mentions the waters (τὰ ὕδατα τὰ Σελινούντια); and they are again noticed in the Itineraries under the name of Aquae Labodes or Labrodes.
The origins of the town's name have been much debated, with Latin "ex acqua", as a reference to the springs of thermal water of the area, or Arabic "Syac", meaning bath, and al Saqquah, dating back to the cult of the Syrian god "Shai al Quaaum", as possibilities.
The city walls, the bastions and the Old Castle owe their existence to Roger the Great Count.
A royal city which had remained faithful to Manfred of Sicily during the Angevine invasion, by 1268 A.D. it was besieged by Charles I of Anjou and surrendered the following year. After the Sicilian Vespers, it established itself as a free commune. During the Aragonese-Angevine wars it was besieged numerous times, after which the Peralta family took possession of it and obtained by the king of Sicily the right to mint coins. In the following centuries the town was at the center of bloody feuds between rival baronial families (the Luna, of Aragonese origin, and the Perollo, of Norman stock), which nearly halved its population. In 1647 the impoverished town was the seat of an anti-Spanish rebellion.
During World War II the Italian Regia Aeronautica (Royal Air Force) had a base near Sciacca.
The municipality borders Caltabellotta, Menfi, Ribera and Sambuca di Sicilia.
Sciacca still retains much of its medieval layout, which divided the town into quarters, each laid out on a strip of rock descending toward the sea. Sciacca has several points of interest, including:
Sciacca's festivals include the Carnival, celebrated during the week before the beginning of Lent (February). The highlight of the festival is the parade of bizarre figures mounted on floats, famous throughout Sicily for their gaudy expressions. Sciacca is also the hometown of the Mediterranean Scene.
Starting near the turn of the 20th century, a number of residents of the Sciacca area emigrated to the North End of Boston, Mass.
The economy of Sciacca is mainly based on agriculture, fishing and related food processing industry and tourism.