Internationally renowned Harvard University Professor Arthur Kingsley Porter purchased Glenveagh Castle and the surrounding property from the Adair estate in 1929. Porter and his wife Lucy used it as a second home, displayed his significant art collection, and entertained guests. Porter also built a fishing cottage on Inishbofin Island. He disappeared mysteriously from that area on 8 July 1933. Porter's widow, Lucy, sold the castle and properties to Henry Plumer McIlhenny of Philadelphia. McIlhenny was a friend and former student of Porter's at Harvard University.