The legal drinking age in Canada is not the same across the country; every province or territory comes up with its own rule book.

In Alberta, Manitoba and Quebec, for example, residents can legally drink once they reach the age of 18; across the rest of Canada, you must be at least 19 years old to legally purchase alcohol.

Those regulations have been in place since the 1970s, when all Canadian provinces and territories lowered the legal drinking age from 20 or 21 to either 18 or 19 to "align more closely with the age of majority."

Ontario and Saskatchewan initially lowered their legal drinking age to 18, but raised it to 19 years of age in the late 1970s after a spike in underage drinking. Prince Edward Island followed suit in 1987.

In this sense, there are two factors that governments weigh when choosing the legal drinking age: the age of majority, and the harmful effects of drinking.

The age of majority in Canada is 18, so provinces such as Alberta may have opted to make the legal drinking age 18 to coincide with the time that individuals are legally recognized as adults.

However, provinces also had to consider the harmful effects of alcohol, according to the Canadian Center for Substance Abuse (CCSA), provinces that have a higher drinking age reduce alcohol consumption in youth and lower traffic crashes.

A Canadian study in 2014 even found that if the drinking age were to be raised to 19 across all of Canada, approximately seven 18-year-old males would be prevented from dying each year.

In this sense, Ontario may have chosen to make the legal drinking age 19 in order to reduce alcohol-related fatalities.

More recently, Canadian provinces have also introduced different legal ages for cannabis consumption, ranging from 18 years of age in Alberta to 21 in Quebec as of October 2019.