On April 18, 1906, Katherine Duer Mackay, wife of industrialist and art collector, Clarence Mackay, wrote a letter to Mr. Ordronaux, Churchwarden of Trinity Episcopal Church, stating,”McKim, Meade and White, of New York, are making plans for the construction of a new church, for certain alterations to the rectory and a cloistered passage.” Mrs. Mackay envisioned the church as a memorial to her mother Ellin Travers Duer while the parish house was erected in memory of her father, William Alexander Duer. Stanford White, partner of the architectural firm, had designed the Mackay’s palatial estate, Harbor Hill immediately to the south of Trinity. One of the most accomplished architects of the era and a partner in the most important firm of the day, Stanford White designed comparatively few churches and the Roslyn commission was unfortunately, destined to be his last. White’s design is derived from transitional Norman-Early English Style of the 14th century with its’ use of round-arched windows and bell cote, or belfry wall.

The building is characteristically cruciform in plan and built in the traditional manner with roof-trusses supported by walls and buttresses. The interior is dominated by the superb framing of the high vaulted roof which employs ponderous soaring wooden trusses in the English Medieval tradition. Stained glass windows, many executed by Tiffany studios and commissioned by the Mackays are found throughout the building.