anglesey (; ) is an island off the north-west coast of wales forming the mainland of a principal area (under the name isle of anglesey) and historic county of the same name, which includes holy island to the west and some islets and skerries. anglesey island, with an area of , is by far the largest island in wales, seventh largest in the british isles, largest by area in the irish sea and second most populous after the isle of man. the local government area of isle of anglesey county council measures , with a population at the 2011 census of 69,751, of whom 13,659 live on holy island. the menai strait between anglesey and mainland wales is spanned by the menai suspension bridge, designed by thomas telford in 1826, and by the britannia bridge, built in 1850 and replaced in 1980. the largest town is holyhead on holy island, where the port handles over 2 million passengers a year to the republic of ireland. the next largest town is llangefni, seat of the county council. from 1974 to 1996 anglesey was administered as part of gwynedd. most of anglesey's inhabitants are welsh speakers. , the welsh name for the island, is used for the uk parliament and national assembly constituencies. the island is in the ll postcode area (ll58–ll78).