The Notre-Dame Basilica is located in the historic district of Old Montreal, Quebec. It is located next to the Saint-Sulpice Seminary and faces the Place d'Armes square.
The basilica was designed by James O'Donnell, an Irish-American Anglican from New York City, a proponent of the Gothic Revival architectural movement. The main construction work took place between 1824 and 1829. The cornerstone was laid at Place d"Armes on September 1, 1824. The sanctuary was finished in 1830, and the first tower in 1841, the second in 1843. On its completion, the church was the largest in North America. It remained the largest in North America for over fifty years. The vaults are colored deep blue and decorated with golden stars, and the rest of the sanctuary is decorated in blues, azures, reds, purples, silver, and gold. It is filled with hundreds of intricate wooden carvings and several religious statues. Unusual for a church, the stained glass windows along the walls of the sanctuary do not depict biblical scenes, but rather scenes from the religious history of Montreal. In 1886 Casavant Frères began building a new 32-foot pipe organ with 7000 individual pipes, four keyboards, 92 stops using electro-pneumatic action at the church, completing it in 1891.
Because of the splendor and grand scale of the church, a more intimate chapel, Chapelle du Sacré-Cœur (Chapel of the Sacred Heart), was built behind it, along with some offices and a sacristy. It was completed in 1888.