The original Mary Gallagher, the subject of a popular song, was courted by a young man just returned from America but her parents refused to let them marry and he left to return to where he had made his wealth on October 6th 1861. The previous year some of her family had gone to New Zealand when 286 adults and 49 children were evicted from the Glenbeigh estate. On December 5th 1861 she emigrated to join her counsins. On the boat she met and married Donal Egan. She gave birth to a baby but died within four months while her son only survived a few more months. The tragic love story was made into a song by a local stone mason and when recorded in 1968 by the Emmet Spiceland group it gained wide popularity and became the theme of the Festival.

Each year great crowds come to the Donegal town where the streets are filled by traditional musicians. A highlight is a concert by local singer Daniel O'Donnell and the choice of Mary from the international entrants.