Jubilant customers stood in long lines for hours then lit up and celebrated on sidewalks as Canada became the world's largest legal marijuana marketplace.

Key points: Ian Power is the first man to purchase marijuana for recreational use

Ian Power is the first man to purchase marijuana for recreational use Canada intends to pardon everyone with past convictions for possessing up to 30 grams

Canada intends to pardon everyone with past convictions for possessing up to 30 grams Ontario, the nation's most populous province, won't be opening stores until after July 2019

In Toronto, people smoked joints as soon as they rolled out of bed in a big "wake and bake" celebration.

In Alberta, a Government website that sells pot crashed when too many people tried to place orders.

And in Montreal, Graeme Campbell welcomed the day he could easily buy all the pot he wanted.

"It's hard to find people to sell to me because I look like a cop," the clean-cut, 43-year-old computer programmer said outside a newly opened pot store.

He and his friend Alex Lacrosse were smoking a joint when two police officers walked by.

"I passed you a joint right in front of them and they didn't even bat an eye," Mr Lacrosse told his friend.

Festivities erupted throughout the nation as Canada became the largest country on the planet with legal marijuana sales.

People celebrated at midnight in Toronto to mark the first day of the legalisation of cannabis. ( AP: Chris Young/The Canadian Press )

At least 111 pot shops were expected to open across the nation of 37 million people, with many more to come, according to an Associated Press survey of the provinces.

Uruguay was the first country to legalise marijuana.

Ian Power was first in line at a store in St John's, in the province of Newfoundland, but didn't plan to smoke the one gram he bought after midnight.

Ian Power and Nikki Rose pose with the receipt for the first legal cannabis for recreational use sold in Canada. ( AP: Paul Daly/The Canadian Press )

"I am going to frame it and hang it on my wall," the 46-year-old Mr Power said.

"I'm going to save it forever."

Tom Clarke, an illegal pot dealer for three decades, opened a pot store in Portugal Cove, Newfoundland, and made his first sale to his dad. He was cheered by the crowd waiting in line.

"This is awesome. I've been waiting my whole life for this," Mr Clarke said.

"I am so happy to be living in Canada right now instead of south of the border."

Canada to pardon past small weed convictions

The start of legal sales wasn't the only good news for pot aficionados: Canada said it intends to pardon everyone with convictions for possessing up to 30 grams of marijuana, the newly legal threshold.

"I don't need to be a criminal anymore, and that's a great feeling," Canadian singer Ashley MacIsaac said outside a Government-run shop in Nova Scotia.

"And my new dealer is the Prime Minister!"

Canadian Prime Minister Justin Trudeau said the legalisation takes "profits out of the hands of criminals". ( AP: Adrian Wyld/The Canadian Press )

Medical marijuana has been legal since 2001 in Canada, and Prime Minister Justin Trudeau's Government has spent the past two years working toward legalising recreational pot to better reflect society's changing opinion about marijuana and bring black market operators into a regulated system.

Corey Stone and a friend got to one of the 12 stores that opened in Quebec at 3:45am to be among the first to buy pot. Hundreds later lined up.

"It's a once-in-a-lifetime thing — you're never ever going to be one of the first people able to buy legal recreational cannabis in Canada ever again," Mr Stone, a 32-year restaurant and bar manager, said.

The stores have a sterile look, like a modern clinic, with a security desk to check identification.

The products are displayed in plastic or cardboard packages behind counters.

People look to purchase cannabis products at the Quebec Cannabis Society Store in Montreal. ( Reuters: Christinne Muschi )

Buyers can't touch or smell the products before they buy. A small team of employees answer questions but don't make recommendations.

"It's a candy store, I like the experience," Vincent Desjardins, a 20-year-old-student who plans to apply for a job at the Montreal shop, said.

Canadians can also order marijuana products through websites run by provinces or private retailers and have it delivered to their home by mail.

At 12:07am, the Alberta Liquor and Gaming Commission tweeted: "You like us! Our website is experiencing some heavy traffic. We are working hard to get it up and running."

Alberta and Quebec have set the minimum age for purchase at 18, while other provinces s have made it 19.

Stores won't be operating in Ontario until spring

No stores will open in Ontario, which includes Toronto.

The nation's most populous province is working on its regulations and doesn't expect stores to operate until spring.

While retail sales won't begin in Toronto until August next year, locals are making the most of the relaxed laws. ( AP: Chris Young/The Canadian Press )

A patchwork of regulations has spread in Canada as each province takes its own approach within the framework established by the Federal Government.

Some provinces have Government-run stores, others allow private retailers, and some have both.

Canada's national approach allows unfettered banking for the pot industry, inter-province shipments of cannabis and billions of dollars in investment — a sharp contrast with prohibitions in the United States, where nine states have legalised recreational sales of pot and more than 30 have approved medical marijuana.

Bruce Linton, CEO of marijuana producer and retailer Canopy Growth, claims he made the first sale in Canada — less than a second after midnight in Newfoundland.

"It was extremely emotional," he said.

"Several people who work for us have been working on this for their entire adult life and several of them were in tears."

Mr Linton is proud that Canada is now at the forefront of the burgeoning industry.

"The last time Canada was this far ahead in anything, Alexander Graham Bell made a phone call," said Mr Linton, whose company recently received an investment of $4 billion from Constellation Brands, whose holdings include Corona beer and Robert Mondavi wines.

AP