Westmount was first incorporated as a city in 1874 (as the Village of Côte St-Antoine, and later the Town of Côte St-Antoine).
On January 1, 2002, as part of the 2002–2006 municipal reorganization of Montreal, it was merged into the city of Montreal and became a borough. However, after a change of government and a 2004 referendum, it was re-constituted as an independent city on January 1, 2006. Nevertheless, it remains part of the urban agglomeration of Montreal and the bulk of its municipal taxes go to the Agglomeration Council, which oversees activities common to all municipalities on the Island of Montreal (e.g. fire protection, public transit) even after the demerger.
Traditionally, the community of Westmount was an enclave of wealthy anglophones of British ancestry, having been at one point the richest community in Canada; it now competes with West Vancouver in British Columbia, Forest Hill, Rosedale, and The Bridle Path, in Toronto for the title. This made the city one of several symbolic targets of FLQ terrorist bombings in the 1960s, culminating in the 1970 October Crisis. However, it is now mostly inhabited by middle and upper-middle class families of multiple ethnic and linguistic backgrounds with the stereotype only partially existing at the very top of the mountain, around Summit Circle, a road which rings around its summit (one of the three peaks of Mount Royal), and on which some of Montreal’s wealthiest families (including the Bronfmans and the Molsons) have built their homes as well as select avenues located off The Boulevard.
As of the Canada 2011 Census, the population was 19,931.
The income per-capita for a household is $210,120 one of the highest in North America. The largest occupation categories were 33.0% employed in management occupations, 20.3% in business, finance, and administration occupations, and 15.4% in social science, education, government service and religion occupations.
There were 8,460 households out of which 26.2% had children living with them, 47.5% were married couples living together, 6.7% had a female lone-parent as a householder, and 35.5% of all households were made up of individuals. The average married-couple family size was 3.1.
In the city the population was spread out with 15.7% under the age of 15, 11.9% from 15 to 24, 22.9% from 25 to 44, 28.6% from 45 to 64, and 20.8% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 83.7 males. For every 100 females age 15 and over, there were 80.2 males.
About 27% of the population is foreign-born, most having immigrated since 1991. Visible minorities constitute 14% of the population (Chinese 3%, Arab 2.8%, Latin American 2.1%, West Asian 1.6%, South Asian 1.3%). Residents declared their religions as Catholic (31.0%), Protestant (21.5%), Christian Orthodox (3.7%), Jewish (3.2%), Muslim (2.7%) and other Christian (1.9%).