The population had grown from 9,000 inhabitants around 1800 to 23,000 in 1825, then to 58,000 in 1852. As of 1831, the majority of Montréal’s population was of British origin. This new ethnic mix was noticeably reflected in the urban landscape: English and Scots dominated in the West, the Irish were concentrated in the Southwest, while the East was Canadien territory.

Ethnic tensions reached the boiling point in the 1830s, when the Patriotes led a political struggle culminating in the Rebellions of 1837 and 1838. The military repression of the Rebellions confirmed the victory of the Tories, who represented English-speaking Montrealers.

A more clearly-defined hierarchy was being established between the commercial bourgeoisie, controlled by the British and the Scots, and local, French-speaking merchants.

The number of craftsmen grew quickly. Most Irish immigrants were labourers or servants, who in turn were primarily women and teenage girls. This population would later form the base of Montréal’s industrial working class.

Immigration also intensified religious diversity. The city filled with churches, mostly Protestant, but the Canadiens and the Irish formed a Catholic majority. The Catholic Church’s intention to create a new diocese in Montréal, separate from the one in Québec City, became a reality in 1836. In the meantime, the Sulpicians built a new place of worship, Notre-Dame Church.