The prehistory of Sicily, well before the Greeks arrived is still to this day shrouded in some mystery. We are left with a written tradition from a number of Greek writer but they were writing about a past some thousand years before their time. Modern attempts at understanding this period are even debated, which leaves us with our best guesses based off of what is found in modern research and what the ancients say.
The Island of Sicily west of Greek lands would come into the Greek periphery as the Mediterranean was emerging out of the Dark Ages. Trade would once again begin to flow from the west as it had done during the Bronze Age to the Mycenaeans. Though, with the collapse of the Bronze Age much of this trade would be disrupted as various civilisations went into decline or disappeared completely.
Though, as trade began increasing, more Greek cities would have been setting up their own trading connections at Sicily. Eventually, the various Greek city states would send out expeditions to found colonies on the island. This would provide relief with the over population problem that was beginning to occur in some of the larger cities, while also opening up more markets to the Greek mainland.
The Greeks were not the only people present on Sicily, with it home to three separate indigenous cultures according to the written tradition. Also present was that of the Phoenicians, a civilisation originating in the Levant and the founders of the famous city of Carthage. They were also engaging in trade and establishing their own colonies. All these different peoples would for the most past during the 8th century BC, co-exist peacefully, but as time went on and more colonies emerged, interests would start to be encroached upon.
Maps of Sicily