Ordnance Survey reference SJ 050662.
The foundation stone of the new church, which was intended to replace St. Hilary's, was laid on 6 July 1871.
The consecration service was due to take place on 29 January 1874; but on 27 January, the Bishop of St.Asaph announced that he would not conduct the ceremony, because he considered that a panel of the reredos "had a somewhat ritualistic tendency" - i.e. it depicted a Crucifix instead of a Cross. Eventually the panel was removed, and after a delay of almost two years, the Bishop consecrated the church on Tuesday, 7 December 1875. There was further controversy during the service.
St. Mary's now acts, to all intents and purposes, as the parish church of Denbigh.
The Clwyd FHS website has a photograph of the church.