Barrow's population reached a second peak in of 77,900 in 1951; however, by this point the long decline of mining and steel-making as a result of overseas competition and dwindling resources had already begun. The Barrow ironworks closed in 1963, three years after the last Furness mine shut. The by then small steelworks followed suit in 1983, leaving Barrow's shipyard as the town's principal industry. From the 1960s onwards it concentrated its efforts in submarine manufacture, and the UK's first nuclear-powered submarine, , was constructed in 1960. , the , and s all followed. The last of these are armed with Trident II missiles as part of the British government's Trident nuclear programme.