The
See is maintained in the
Roman Catholic Church, but was abandoned in the
Church of Ireland. Following an Act of Parliament of 1833, the See of the established church was merged with that of the
Diocese of Killala and Achonry.
Middle Ages The pre-
Reformation diocese at various moments absorbed other local episcopal sees deriving from Celtic monastic jurisdictions. The
diocese of Annaghdown was created c. 1179. Although not listed in Rathbreasail or Kells, Annaghdown diocese survived nonetheless for many centuries through monastic outreach from
Annaghdown Abbey. Several 'bishops of Annaghdown', from 1189 to 1485, were systematically elected by its 'Cathedral Chapter' and, despite many counterclaims from Tuam, some were approved by Rome. In 1485, when the Wardenship of Galway was created, Annaghdown was formally united with Tuam by
Papal decree, and some of its parishes,
Claregalway,
Moycullen and
Shrule, were formally attached to the new wardenship. The
diocese of Mayo, though recognised officially in the Synod of Kells, was suppressed in 1202. However, bishops of Mayo were continued to be appointed as late as the 16th century. One of its bishops,
Patrick O'Hely, who died in 1589, is numbered among the Irish martyr saints. The diocese was formally joined to Tuam by Papal decree in 1631. Even after the Synod of Kells, a multiplicity of abbeys had pastoral care for the people in their surroundings. With the despoliation of the monasteries and the scarcity of priests during penal days, old churches were abandoned. When they were replaced, it was with miserable thatched shelters. House 'stations' were a necessary substitute for normal public worship.
Lordship of Ireland Ireland's political scene and ecclesiastical was changed permanently by the coming of the
Normans and the influence of the English Crown. With the
English Reformation, church property was forfeited by the state and transferred to the official state religion – the
Church of Ireland. Although only a winning over a minority of the people, despite the many political and economic advantages offered by conversion to the state religion, all subjects of the Crown were obliged, in their taxes to support the official state church. Additionally, the
Penal Laws sought to curb or altogether extinguish the practice of the Roman Catholic religion amongst the majority population of the Archdiocese.
19th and 20th centuries In 1825, Archbishop Kelly testified before a
House of Commons Committee of enquiry that out of 107 places of worship in the diocese, only eighteen had slated roofs. The others, he said, were thatched and wretched, insufficient to contain the congregations, and in many instances the public prayers were celebrated in the open air. The chapels were also used as Sunday schools, and a great many were used on weekdays as the local school. As persecution abated, and as priests became more plentiful, a new confidence grew and the small thatched buildings were superseded by more solid, ample structures. Only two of the existing churches in the diocese predate 1800 - the abbeys of
Ballyhaunis and
Ballintubber. But from 1820 onwards, a phenomenal rate of construction began. Twenty of the 135 existing churches were constructed in the Famine years, 1840–1850. The pattern of church replacement or reconstruction continued to modern times. Modern church architecture is rare in Tuam diocese, as most churches predate modern times. The four special chapels constructed at Knock Shrine, including the Basilica, since 1972 are, however, of special importance.
Population changes In 1800 there were no more than one hundred priests in the archdiocese. The number grew steadily to 170 about 1968; despite the fact that the population dropped to less than 30% of what it was before the Famine. In 1986, the figure attending Mass in the archdiocese was approximately 75% of the whole Catholic population, or 89% of those obliged to attend Mass. This has decreased by approximately 10% in recent years. A major survey of the diocese carried out in 1996 found that the pattern of the population decline is still continuing; nowadays, however, that decline continues through out-migration to the eastern part of Ireland, but with the same deleterious effects on the west. As of 2016, there were 103 priests in the archdiocese, with 69 over the age of 60 and 20 over the age of 80. ==Education in the diocese==