Canada has become the second country after Uruguay to legalise possession and use of recreational cannabis.
The nationwide market for cannabis opened on Wednesday at midnight amid lingering questions about the impact on health, the law and public safety.
Preparations included mailings to 15m households detailing the new cannabis laws and public awareness campaigns.
But there remain concerns, including about the readiness for police forces to tackle drug impaired driving.
Canadian provinces and municipalities have been preparing for months for the end of cannabis prohibition.
Provinces and territories are responsible for setting out many of the details for where cannabis can be bought and consumed within their jurisdictions.
This has created a patchwork of legislation across the country as jurisdictions choose more or less restrictive frameworks for selling and using cannabis.
Shops in the province of Newfoundland, the most easterly time zone in Canada, opened as midnight struck for the first legal sales of cannabis in the country.
How ready is Canada for cannabis?
There remain unanswered questions on some key issues around how legal cannabis will work in Canada.
A number of analysts are predicting a shortage of recreational marijuana in the first year of legalisation as production and licensing continues to ramp up to meet demand.
Ontario, Canada’s most populous province, will only begin opening retail stores next spring, though residents will be able to order cannabis online.
British Columbia, one of the provinces with the highest rates of cannabis use, will only have one legal store open on Wednesday.
Until retail locations are more widely available, some unlicensed cannabis retailers, which have flourished in the years since the law was first proposed, may stay open.
It is unclear if police will crack down on them immediately, or if they will turn a blind eye.
The change in national drug policy has also created headaches with the US, where the drug remains federally a controlled substance.
On Tuesday, the US Customs Border Protection Agency said border guards will have “broad latitude” to determine who is admissible to the country.
Border guards may ask Canadians if they smoke pot, and deny them entry if they believe they intend to do so in the US.
Canada has also been rolling out signs at all airports and border crossings to warn travellers that crossing international borders with the drug remains illegal.