But outside their homes, there are few places where those customers can legally smoke it.

Clouds of pot smoke float around North America's biggest cities, but for the most part it's not allowed in public spaces, and there hasn't been a profusion of Amsterdam-style coffee shops or other businesses where someone can consume a legal drug.

But that could be changing.

Denver's first legal consumption lounge, The Coffee Joint, opened last year. Its co-owner Rita Tsalyuk described it as a "Starbucks on steroids". It costs $5 to enter if you plan to consume – though entrance is otherwise free – and while the shop itself can't sell cannabis, it's attached to a licensed dispensary. The space hosts video game and movie nights, singles mixers, yoga and industry events.