The Assumption Church has been associated with a Jesuit Huron mission at La Pointe du Montréal, the parish of L'Assumption du Détroit, since 1761. The current church replaced an earlier one, Notre Dame de L'Assomption, built on a nearby site in 1785. When the present church building was constructed, it was the major edifice built by the Church of Rome in Upper Canada.
Designed by Detroit architect Robert (sometimes known as Richard) Elliot, it is built in the Perpendicular Gothic style with picturesque details. Jacques Reaume was the master mason. The plan is symmetrical with a central tower and spire, nave and aisles and with no clerestory. The transepts that accommodated chapels were removed in 1907. The bricks were made with a new brick-making machine invented by Collins of Sandwich, now part of Windsor. The tower and sanctuary, which were part of the original design, were added in 1874. The altar, made of painted Caen stone, dates from 1887. The wood pulpit, classically designed and Baroque in character, resembles those found in 18th-century Quebec churches. Salvaged from the earlier church (1787), the pulpit was built by a woodcarver named Frérot. The patterned coloured glass windows in the main part of the church were erected in 1882; the pictorial stained glass windows of the sanctuary and apse are believed to have been installed in 1874. The picturesque quality of the architecture is accentuated by its landscaped setting when viewed from the north and west.
In 1978, the City of Windsor designated the church under the Ontario Heritage Act and, in 1985, the Ontario Heritage Trust secured a heritage easement on the building.