[1] The cathedral, located on Castle Street opposite Conwal Parish Church in the town, celebrated its centenary in 2001.

The cathedral is named for the Saints Adamnán and Columba; it opened on 16 June 1901 and is built in Victorian neo-Gothic style on a site overlooking the town.

They carry the names of the saints of Tír Conail - Dallan, Conal and Fiacre, Adomnán, Baithen and Barron, Nelis and Mura, Fionán and Davog, Cartha and Caitríona, Taobhóg, Cróna and Ríanach, Ernan and Asica and Columba.

After the cathedral was opened the organist played "O'Donnell Abu", "St Patrick's Day", "The Last Rose of Summer", "The Wearing of the Green" and "The Bells of Shandon".

[9] During the COVID-19 pandemic, Monsignor Gillespie, with Bishop of Raphoe Alan McGuckian, agreed to celebrate weekday morning Mass for the nation on RTÉ Television.

[11] The Reverend Damien Nejad, of Hiberno-Iranian origin, has a particularly interesting background as he was the first diocesan priest ordained in Ireland to have a Persian family; The Reverend Nejad was born to an Iranian Muslim father and a Catholic mother, originally from Annagry, in, and later grew up in, Glasgow and was baptised at his own request when he was six.

It is not definitively known when the original building was constructed; however, during reconstruction work in 1988, a slate bearing a mason's mark from the year 1850 was discovered.

Barry Feely from County Roscommon designed the chapel's granite altar; this is situated in front of a stained glass window which displays the "Virgin of the Sign" icon.