There are more than fifty uninhabited islands greater in size than in the Outer Hebrides, including the Barra Isles, Flannan Isles, Monach Islands, the Shiant Islands and the islands of . In common with the other main island chains of Scotland, many of the more remote islands were abandoned during the 19th and 20th centuries, in some cases after continuous habitation since the prehistoric period. More than 35 such islands have been identified in the Outer Hebrides alone. On Barra Head, for example, Historic Scotland have identified eighty-three archaeological sites on the island, the majority being of a pre-medieval date. In the 18th century, the population was over fifty, but the last native islanders had left by 1931. The island became completely uninhabited by 1980 with the automation of the lighthouse.