In the 12th century, the Irish Church moved towards a parochial model, and following restructuring under figures such as St. Malachy, Archbishop of Armagh, and the papal legate Cardinal Paparo in 1152, thirty-eight dioceses, each comprising a number of parishes, were approved.
Henry II of England visited Dublin in 1172 and founded a branch of the Knights Templar, granting them lands including "the Vill of Clumtorf".
The last prior, Sir John Rawson, was made Viscount Clontarf, with a pension, a seat in Parliament and a grant of the commandery as his manor house.
In one related further series of events, Cromwell gave the former commandery and lands to a man named Blackwell, for military service and in return for a yearly rent of one shilling, and he transferred them to Captain (or Admiral) John Vernon.
The Vernon family were able to hold their place even after the Restoration, and they built the core of the current castle in the 19th century, prior to its sale in the 1930s and the subsequent development of its land, with the main building expanded as a hotel.
Notably, for almost this entire period, Clontarf had no Catholic place of worship, the first church, a small chapel dedicated to St. John the Baptist, being built only in 1825.
Callanan applied in the early 1830s to Clontarf's leading landowner, Colonel Vernon, for a site for a larger church, suggesting that the locality known and mapped as "the Sheds" would be suitable.
This area of small lanes and mud cabins held around 200 families, mostly working in the fishery, and the Vernons were keen to improve it, so they offered a 99-year lease if the parish priest could clear it.
Having paid monetary compensation to the other families, Callanan secured the offered land and the foundation stone of the Church of St. John the Baptist was laid in 1835 (when the curate William Walsh, eventually Archbishop of Halifax, left the parish, replaced by a Fr.
The land for this was provided rent-free by Sir Compton Domville (of Santry Demesne) and the construction, finished in 1848, funded by a James Coughlan.
The church was officially opened in 1864 by the Roman Catholic Archbishop of Dublin, Paul Cullen, and there are fuller details in the relevant article.
In 1890, the Sisters of the Holy Faith opened a convent in Clontarf, with schools for young ladies and small boys, supported by a Miss Allingham, whose brother then sponsored an extension to the church and many fittings, to a cost of 6,000 Irish pounds.
In 1901, a new lease for the schools for boys and girls (on Vernon Avenue) was obtained and Miss Allingham, who had also funded further work on the church, provided around 2,000 pounds to enlarge and equip them.
In 1925, Canon Dempsey, the parish priest, bought the old Clontarf Town Hall, from the area's brief spell as an autonomous incorporated township, reopening it as a chapel-of-ease to the main church, dedicated to St. Anthony of Padua.