Throughout Antiquity, the city was relatively unimportant. According to one legend, the city was founded as a colony from Argos, while another holds that it was founded, along with Side and Aspendos, by the seers Mopsos, Calchas and Amphilochus after the Trojan War. The city is first mentioned in c. 500 BC by Pseudo-Scylax (polis Sylleion). From 469 BC, the city (as Sillyon) became part of the Athenian-led Delian League. It is mentioned in the Athenian tribute lists in c. 450 BC and again in 425 BC, and then disappears again from the historical record until 333 BC, when Alexander the Great is said to have unsuccessfully besieged it. According to Arrian (Anabasis Alexandri I. 26), the site (recorded as Syllion) was well-fortified and had a strong garrison of mercenaries and "native barbarians", so that Alexander, pressed for time, had to abandon the siege after the first attempt at storming it failed. The city was extensively rebuilt under the Seleucids, especially its theatre. In later times, when most of western Asia Minor fell to the Kingdom of Pergamon, Sillyon remained a free city by a decision of the Roman Senate. The city has an attested continuous tradition of minting its own coins from the early 3rd century BC up to the reign of the Roman emperor Aurelian in the 270s. Silver tetradrachms of the Alexandrian and Lysimachian types were minted between 281 and 190 BC, but other than that, the city's coinage is in bronze. 3rd-century BC coins feature a bearded head or a standing figure, possibly identifiable with Apollo, or a lightning and the inscription ΣΕΛΥΝΙΥΣ (the native Pamphylian name). Coinage under Roman suzerainty featured the same motifs, but with the inscription hellenized to CΙΛΛΥΕΩΝ ("of the Sillyeans").
