MONTREAL — Canada on Wednesday became the first major world economy to legalize recreational marijuana use, beginning a national experiment that will alter the country’s social, cultural and economic fabric, and present the nation with its biggest public policy challenge in decades.

Newfoundlanders became the first Canadians to be able to smoke pot legally, when retailers there opened in the country’s easternmost province at midnight.

Across the rest of the country, government-run stores were preparing to greet consumers, who will be able to choose among pre-rolled joints, fresh or dried marijuana flowers and cannabis oil — all of which are permitted under the new federal law.

And pot enthusiasts from Montreal to Winnipeg to Calgary were getting their bongs ready for “End of Prohibition” house parties.