Crowds were serenaded by live music as they waited for the nation's first legal recreational pot shops to open. They ate doughnuts and funnel cakes as a glass-blower made smoking pipes. Some tourists even rode around in a limo, eager to try weed but not so eager to be seen buying it.

And when the sales began, those who bought the drug emerged from the stores, receipt held high, to cheers.

"I'm going to frame the receipt when I go home, to remind myself of what might be possible: Legal everywhere," musician James Aaron Ramsey, 28, who did some time in jail for pot possession in Missouri and played folk tunes with his guitar for those in line.

Activists hope he's right, and that the experiment in Colorado will prove to be a better alternative to the costly American-led drug war, produce the kind of revenue that state officials hope and save the government costs in locking up drug offenders.

Washington state will open its pot industry later this year. Both states programs will be watched closely not just by officials in other states, but by activists and governments in other countries because the industries will be the first to regulate the production and sale of the drug.

Some countries have decriminalized the drug, and the Netherlands lets people buy and sell it, but it's illegal to grow or process it.

Just as shops opened Wednesday, the Denver police department tweeted, "Do you know the law?" and linked to city websites on state and local laws that include bans on public consumption, driving under the influence, taking marijuana out of state and giving pot to anyone under 21.

At least 24 pot shops in eight towns opened, after increasing staff and inventory and hiring security.

Shopper Jacob Elliott traveled from Leesburg, Va., to be among the first to buy legal pot. He said he wrote reports in college about the need to end prohibition of marijuana, but never thought it could happen in his lifetime.

"This breaks that barrier," he said.

Addison Morris, owner of Rocky Mountain Mile High Tours, had 10 clients waiting inside a limo who paid $295 for three hours of chauffeuring by a "marijuana concierge" who would help them choose strains and edible pot products.

"We're your grandmother's pot connection," the 63-year-old said. "We're not the hippie stoners who are going to stand in this cold and party."

Morris said she's booked through the end of February with out-of-state clients. Guests receive samples in designer bags before getting tours. She said she's selling discretion. Guests are asked to leave cameras at home.

Earlier, pot users welcomed the new year — and the new industry — by firing up bongs and cheering in a cloud of marijuana smoke at a 1920s-themed "Prohibition Is Over" party in downtown Denver.

Skeptics worry the industry will make the drug more widely available to teens, even though legal sales are limited to adults over 21. They fear that the increased availability will lead to a rise in drug abuse and crime.

Preparation for the retail market started more than a year ago, soon after Colorado voters in 2012 approved the legal pot industry. Washington state has its own version, which is scheduled to open in mid-2014. Uruguay passed a law in December to become the first nation to regulate pot.

Pot advocates, who had long pushed legalization as an alternative to the lengthy and costly global drug war, had argued it would generate revenue for state coffers and save money in locking up drug offenders.

Still, setting up regulations, taxation and oversight for a drug that's never been regulated before took some time.

Colorado set up an elaborate plant-tracking system to try to keep the drug away from the black market, and regulators set up packaging, labeling and testing requirements, along with potency limits for edible pot.

The U.S. Justice Department outlined an eight-point slate of priorities for pot regulation, requiring states to keep the drug away from minors, criminal cartels, federal property and other states in order to avoid a federal crackdown. Pot is still illegal under federal law.

Denver International Airport placed signs on doors warning fliers they can't take the drug home in their suitcases.

With the additional police patrols, the airport warnings and various other measures, officials hoped they have enough safeguards in place to avoid predictions of public health and safety harm from the opening of the pot shops.

There was no shortage of skeptics worried retail pot would endanger the public. A group of addiction counselors and physicians said they're seeing more marijuana addiction problems, especially in youths, and that wider pot availability will exacerbate the problem.

"This is just throwing gas on the fire," said Ben Cort of the Colorado Center for Dependency, Addiction & Rehabilitation at the University of Colorado Hospital.

Not all marijuana users in Colorado are toasting the dawn of retail sales.

Some medical marijuana patients groups say they're worried about supply. That's because the retail inventory for recreational use is coming entirely from the preexisting medical inventory. Many in the industry warned patients to stock up before the sales began.

It was too soon to tell whether prices were going up.

For now, medical patients should have plenty of places to shop. Most of Colorado's 500 or so medical marijuana shops haven't applied to sell recreational pot, and many that have plan to serve both recreational and medical patients

Marijuana activists were hoping Colorado's grand experiment wouldn't be that noticeable after an initial rush of shopping.

"Adults have been buying marijuana around this country for years," said Mason Tvert, spokesman for the Marijuana Policy Project. "The only difference is that in Colorado they will now buy it from legitimate businesses instead of the underground market."