A group of islands in the Firth of Lorn (Argyll and Bute), the Slate Islands are located 13 miles (21 km) southwest of Oban. These islands were the centre of a slate-quarrying industry from the at least the 16th century until the 1960s. Slate was a widely used roofing material throughout the country. Quarries are obvious on several of the islands, as are piers which were used to ship the slate to the mainland.