Keely was born in Thurles, County Tipperary, then a part of the United Kingdom of Great Britain and Ireland on August 9, 1816, to a family in comfortable circumstances.
He arrived at a time when Catholicism in the United States was expanding from its initial footholds in Baltimore, New York City and Boston.
Common practice held that the builder, whether trained as mason or carpenter, crafted his own plans, and details were often executed without even the aid of drawings.
[3] The stained glass was by the Morgan Brothers, thus establishing a business relationship with Keely that carried through a number of projects.
The much-praised work established him as a competent architect and builder at a time when a number of new Roman Catholic churches were being planned "but a relative scarcity of competent architects of the Roman Catholic faith, and Keely's reputation for honesty and integrity quickly made him a popular choice among the hierarchy and clergy throughout the eastern United States.
"[1] Thereafter, Keely effectively became the in-house architect for the Roman Catholic archdioceses and was approached from all sides with requests for designs of churches and other necessary structures for an expanding religious life.
Art historian William Pierson Jr. said of Keely that "... he developed a practice which ultimately became a virtual monopoly in Catholic Church building for more than a quarter of a century.
[6] St. Brigid's on E 8th St. in Manhattan was built in 1848 to a Carpenter Gothic design by Keely, who carved the five-pinnacle reredos, organ case, and wooden altar himself.
Keely designed the Jesuit Church of the Immaculate Conception in the South End of Boston in the style of Italian Renaissance Revival in 1858, as well as its walnut case holding the organ pipe work.
In 2018, in response from objections raised by area residents, the South End Landmarks Commission denied the developer's request to remove the traceries from the side windows of the Church.
[8] Keely also designed the Jesuits Church of the Gesù (Montreal), the college chapel for the Collège Sainte-Marie de Montréal.
[9] Its "twin towers, triple-portal entrance, and rose window inset into a pointed arch reveal a masterful blending of French and English influences.
[15] The three largest cathedrals in New England, Boston and Providence (both still standing), along with Hartford (lost to fire in 1956), were among Keely's greatest accomplishments.
He designed a few churches for Protestant congregations...."[1] Several later noteworthy architects began their careers with Keely's firm, including Elliott Lynch, James Farmer (his wife's brother), James Murphy (his wife's brother-in-law), his son John J. Keely (died 1879, Brooklyn), and son-in-law, Thomas F.
[1] His son, Charles Keely, an architect in his father's firm died in December 1889 at the age of thirty-five of pneumonia, while in Hartford, consulting with the bishop on business.