St. Gregory the Great Roman Catholic Church, in Picton, Ontario, was established in 1837, on land donated by the Rev. William MacAulay, Rector of the Church of England in Picton, St. Mary Magdalene Parish, to his friend, Father Lalor, the Catholic Priest.

The first stone Church was built on the site in 1837, and dedicated by Bishop MacDonnell and Bishop Ganlin in 1839. 

 

The stone Church did duty in The County until 4 September 1892, when Archbishop Cleary laid the corner stone of the present brick Church.

The new Church was dedicated by Archbishop Cleary on 5 October 1893.