DENVER - As Colorado prepares to be the first US state to allow recreational marijuana sales, starting Wednesday, retailers are investing their fortunes into an industry that faces an uncertain future.
Officials, activists and governments around the US and beyond are watching the experiment unfold in Colorado and Washington, where recreational pot goes on sale in mid-2014.
So is the US Department of Justice, which for now is not fighting to shut down the industry.
Will the states be a showcase for a safe, regulated industry that generates hundreds of millions of dollars each year and saves money by not locking up drug criminals, or one that will prove that the federal government has been right to ban marijuana since 1937?
Workers process marijuana at the Medicine Man marijuana dispensary in Denver.(AP Photo)
Over the years, activists and state governments managed to chip away at the ban, their first big victory coming in 1996 when California allowed medical marijuana. Today, 19 other states, including Colorado and Washington, and the District of Columbia have similar laws.
That same year, the Justice Department told federal prosecutors they should not focus investigative resources on patients and caregivers complying with state medical marijuana laws.
In Colorado, the industry took off. Shops advertised on billboards and radio. Denver at one point had more marijuana dispensaries than Starbucks coffee shops. Local officials have since limited such in-your-face ads.
Voters in Colorado and Washington state approved recreational pot in 2012.
The votes raised new questions about whether the federal government would sue to block laws flouting federal drug law.
That didn't happen. In August, the Department of Justice said it wouldn't sue so long as the states met an eight-point standard that includes keeping pot out of other states and away from children, criminal cartels and federal property.
Colorado law allows adults 21 and older to buy pot at state-sanctioned pot retail stores.
Only existing medical dispensaries were allowed to apply for licenses. Only a few dozen shops statewide are expected to be open for recreational sales on New Year's Day.
Toni Fox, owner of 3D Cannabis Center in Denver, anticipates shoppers camping overnight to await her first-day opening. She's thinking of using airport-security-line-style ropes to corral shoppers, and suspects she's going to run out of pot.
"We have to show that this can work," she says. "It has to."
A Colorado State University study estimates the state will ring up $606 million in pot sales next year, and the market will grow from 105,000 medical pot users to 643,000 adult users overnight - and that's not counting tourists.
Legal pot's potential has spawned businesses beyond retail shops. Marijuana-testing companies have popped up, checking regulated weed for potency and screening for harmful molds. Gardening courses charge hundreds of dollars to show people how to grow weed at home.
Dixie Elixirs & Edibles, maker of pot-infused foods and drinks, is making new labels for the recreational market and expanding production on everything from crispy rice treats to fruit lozenges.
"I think it's going to be an exciting time over the next 24 to 48 months," says company president Tripp Keber.
There are still public health and law enforcement concerns, including whether wide availability will lead to more underage drug use and more crime.
To stop the drug from getting smuggled out, regulators in both states are using a radio-frequency surveillance system developed to track pot from the greenhouses to the stores and have set low purchasing limits for non-residents.
Officials concede that there's little they can do to prevent marijuana from ending up in suitcases on the next flight out.
To prevent the criminal element from getting a foothold, regulators have enacted residency requirements for business owners, banned out-of-state investment and run background checks on every applicant for a licence to sell or grow the plant.