The survivor factions were created on the 91st day of the Oceanic Flight 815 survivors on the Island. The factions were led by Jack Shephard and John Locke, as the crew from Naomi's freighter began coming to the Island. The split was based on a difference of opinion on whether the freighter crew were coming to rescue them (as Jack believed), or for more nefarious unknown reasons (as Locke believed). ("The Beginning of the End")