The text below is taken from the Heritage Newfoundland & Labrador web site.
Built between 1835 and 1836, St. Thomas' Anglican Church in St. John's is purported to be the oldest Anglican church in Newfoundland. Land for the church was secured from the British government with the help of Governor Sir Thomas Cochrane. Cochrane insisted the grant be contingent upon seats being reserved for church-going members of the local garrison. With land secured, Archdeacon Edward Wix went to England in 1833 on a fund-raising tour.
The approximate £2,000 he raised was sufficient to build the church. The church initially measured 19m. (62 ft) long by 11m. (36 ft) wide with galleries and had a seating capacity of 700. Catholic Irishman Patrick Keough designed and built St. Thomas'. His previous works in St. John's had included Government House, Presentation Convent, and the "Stone Cottage" at 16 Harvey Street. Outside the capital he had designed the Court House in Harbour Grace.
Built from local spruce and pine, with Gothic windows and other Gothic motifs, St. Thomas' is an excellent wooden example of early Gothic revival architecture in British North America. One of its distinguishing features, which sets it apart from other early Gothic churches in British North America, is its spire. Other structures had the square tower facade, but the steeple did not become common until the 1840s. St. Thomas' tower had its bell imported from England and installed in 1847.
In September 1836 Rev. Charles Blackman of Port de Grave officially opened St. Thomas'. However, it would be another four years before Bishop Aubrey George Spencer consecrated the church. St. Thomas' ceased to be a garrison church after 1871, when the last British military garrison in the colony was closed.
Although the church survived the Great St. John's Fires of 1846 and 1892, the current structure is significantly different from the original. A wind storm in 1846 dislodged the building from its foundations by approximately six inches. The church continued to have a problem with the structure swaying in high winds until 1851, when wings were built on the north and south sides of the building to stabilize it.
Despite the loss of the support from the military garrisons after their removal in 1871, St. Thomas' parish continued to grow and prosper. The church required further additions by 1874 to provide extra seating for a growing congregation and by 1877 the parish was self-supporting.
In 1882 and 1883 renovations improved the building: the chancel was lengthened, and a vestry and an organ chamber were added. The seating capacity was increased to 1300 persons in 1903, when the east end of the church was enlarged. Virtually all the stained-glass windows in the sanctuary date from the 1920s and, in 1934 a carved oak chancel screen was installed.
St. Thomas' Anglican Church became a Registered Heritage Structure in June 1986.