Minimum legal age varies for all kinds of grownup things. Alcohol, tobacco, and cannabis can be 18, 19 or 21, depending on state, province or territory.
Learning to drive is between 14 and 16, with agricultural states tending to allow driving at a younger age. The age of consent is 16 in most US states and throughout Canada. At 18, you can vote and even run for political office in both countries.
When it comes to legal cannabis, the random collection of ages across North America is curious. Every US state that allows recreational cannabis sales requires customers to be at least 21 years old. In Canada the minimum age is 19, except in Alberta (where it’s 18) and Québec (which started at 18 but raised it to 21 earlier this year).
In most jurisdictions, medical marijuana is legal for people age 18 and older, with a doctor’s recommendation.