St. Mary Church was established as a community of the faithful in 1832. It is the oldest Catholic parish in New Haven and the second oldest in Connecticut.

 

Land was purchased near the intersection of York Street and Milford Turnpike Road in New Haven. In 1834, a church was completed on this site and given the name "Christ Church." In 1848, the church was destroyed by fire. Several months after the fire, the property occupied by the Church Street Congregation Society was made available. Plans for building a new church were launched in 1851. Over the next 20 years, this ambitious and impressive edifice developed, designed by James Murphy—at a time when the city's Catholic population was steadily increasing. Built on New Haven's finest residential street, Hillhouse Avenue, St. Mary's represented the faith, the pride, and the high hopes of New Haven's struggling Catholic families. This land had once been used as a turntable for the New Haven & Northampton Railroad along the Canal, and would now be a turnaround for souls, proving to be a place of conversion for many even to this day.

The church was dedicated in 1874, celebrated for its beauty but burdened financially. History of New Haven County, Connecticut, 1892 wrote of St. Mary Church, "It is a fit evidence of the vigor and zeal of the congregation which occupies it." The original plans for a steeple were dropped and the façade of St. Mary's for more than a century featured an un-topped stone tower without belfry or spire. Still, the church was from the first a remarkably handsome, forthright, and lasting symbol of Roman Catholic devotion in the city. 

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St. Mary Church is recognized as a shrine and birthplace of the Knights of Columbus. In 1882, assistant pastor, Fr. Michael J. McGivney, founded the Knights of Columbus, a fraternal benefit society to protect widows and children of working men and foster their faith and social program. Beginning humbly in the church basement with a handful of dedicated lay men, the Knights have miraculously multiplied to 1.6 million members worldwide. On Founders Day, March 1982, the remains of Father McGivney were re-entombed, making the church a shrine for Knights and other pilgrims who visit from all over the world. He was beatified on October 31, 2020. 

 

In 1886, the bishop of Hartford entrusted St. Mary Parish to the Dominican Friars of the Province of St. Joseph. A priory was established at that time to serve the parish and to be the base of a Mission Band of friars who travelled about giving parish missions. Under their energetic administration for 135 years until 2021, St. Mary remained a thriving primary Catholic presence in downtown New Haven.​ Today there remains an active Lay Fraternity of St. Dominic at the parish, and the Dominicans continue to serve from their new priory in New Haven on staff at the Knights of Columbus home office, at Quinnipiac University, at Albertus Magnus College, and as chaplains for the Dominican nuns of the Monastery of Our Lady of Grace in North Guilford, CT. 

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In 1982, in recognition of the 100th Anniversary of the Knights of Columbus, the church went through a complete renovation. Although included in Murphy's original plans, the spire was never completed. The installation of the spire was part of the renovations, courtesy of the Knights of Columbus. Rising 179 feet from the once-stubby tower of the church, the neo-Gothic spire is among New Haven's highest structures. St. Mary Church also underwent massive historic preservation and artistic renovation from February 2019 to September 2020 under the guidance of Pastor John Paul Walker, OP.

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In 2021, St. Mary’s was chosen to be the center of a new archdiocesan plan “because it is perfectly situated to be the geographical and spiritual focal point of a municipal model for New Haven.” The Archdiocesan plan for St. Mary’s called for diocesan priests to serve at St. Mary’s and the seven other churches in New Haven. The friars gifted the parish with a triduum of Masses in November, during which the whole parish family prayed together for the coming transition. Since December 1, 2021, our faithful diocesan fathers have led our dynamic parish with fatherly guidance and spiritual assurance in this new era as a New Haven Catholic parish.