Built between 1840 and 1856, with the belfry and portico as later additions, it has been considered the "flagship cathedral" of the Irish midlands region,[1] Longford's "landmark building"[1][2] and "one of the finest Catholic churches in Ireland".

Work was then delayed by the arrival of the Great Famine, but the church was opened for worship by O'Higgins's successor, Rt.

[6][7] Freezing weather disrupted attempts by firefighters to put out the blaze as their pipes were frozen solid,[1] causing the fire to go on for several hours.

[3] According to Bishop of Ardagh and Clonmacnoise Colm O'Reilly, who had celebrated Midnight Mass in the building hours before the fire began, St Mel's Cathedral was completely destroyed by the fire,[8] describing the cathedral as "just a shell" and "burned out from end to end".

[6] As a result of the fire, Longford parishioners held their Christmas Day masses in the local Temperance Hall.

It was established that the outbreak first arose in an old chimney flue at the rear of the cathedral and broke out into the sacristy through old inspection hatches located behind fitted units.

[21] Among the features of the restored cathedral are a Carrara marble altar sculpted by Tom Glendon, a silver tabernacle created by Imogen Stuart and Vicki Donovan, a pipe organ consisting of 2,307 pipes, built by Fratelli Ruffatti, and stained glass windows designed by Kim en Joong, a Dominican priest.

[21] A silhouette image of St Mel's Cathedral features on the crest of League of Ireland club Longford Town.