Just beyond the Rocky Mountains, an industry that once conjured images of dank basements and back-alley deals is blossoming under state regulation.

After a sluggish start in sales following the 2012 vote to decriminalize marijuana, Colorado’s pot trade — and corresponding tax revenue — is booming as consumers from within and outside the state flock to cannabis shops.

Some predictions made during the campaign by legalization supporters have proved true: Fewer people are being arrested. And despite initial fears that legalization would cause a rampant increase in drug use among Colorado’s youth, teens aren’t smoking more weed, according to the state Department of Public Health and Environment.

But Colorado’s first-in-the-nation dive into a legal pot market also has come with unanticipated problems and failed predictions:

■ Rather than eliminate the black market, legalization of marijuana has helped it flourish, police say.

■ Citations for driving under the influence of pot have made up a bigger portion of DUIs every year since legalization, even as total DUI numbers have dropped.

■ Edible marijuana products were rarely talked about during the Colorado campaign, but they quickly became a headache for lawmakers and hospitals alike.

■ While Colorado’s tourism industry continues to boom, some are linking legal weed to an increase in the homeless population in Denver, which has drawn concerns from downtown convention groups.

■ And some residents of one Colorado community have had enough — and have forced a vote on whether to shut down recreational pot stores in their city.

“Neither side has been exactly right” about legalization’s consequences, said Colorado state Sen. Pat Steadman, who voted for it. “But by and large, all the horrible things that the opponents were afraid of have not come to pass. The sky didn’t fall.”

Still, Colorado’s experience provides plenty of lessons — some cautionary, some encouraging — for voters in Nevada and four other states considering legalizing weed in the Nov. 8 election. A Las Vegas Review-Journal reporter and photographer spent a week in Denver to find out how legalization has affected Colorado and how it might affect Nevada if Question 2 passes.

BLACK MARKET THRIVES

Much like their Colorado counterparts did in 2012, Nevada supporters predict legalizing pot will dry up the illegal drug market.

But after 2½ years of legal sales, Colorado law enforcement officials said the black market is not only still alive, but thriving.

“We’ve seen nothing but black market problems flourishing,” said Jim Gerhardt, vice president of the Colorado Drug Investigators Association. “Marijuana is something people can grow in their home. Little tiny amounts of that can be worth hundreds and thousands of dollars. And really, legalization hasn’t changed any of that.”

Part of the problem, Gerhardt said, is the high price of legal marijuana.

With all the sales, excise and other special taxes mixed in, recreational marijuana bought in Colorado typically carries around a 30 percent tax. So the purchase of a $150 ounce of marijuana at a retail shop can end up costing consumers close to $200.

Gerhardt said that same quality of pot sells for closer to $100 on the street.

Another issue involves growing marijuana. Colorado’s medical marijuana law allows cardholders to grow plants for their use. A cardholder also can act as a “caretaker” for other patients and grow up to 99 plants per patient.

As a result, the amount of marijuana seized in illegal grow cases has skyrocketed.

Denver police seized 524 pounds of marijuana in 2013, the first year it was decriminalized, according to city data. The next year, when retail shops opened, they seized 9,504 pounds. Last year saw a 50 percent drop, with police seizing 4,738 pounds — still well above the 2013 level.

Denver District Attorney Mitch Morrissey said growers are moving to Colorado from across the United States and shipping their products out of the state.

“We’re seeing the products from this state go all over the United States,” he said.

The issue boiled over in December 2014 when neighboring states Nebraska and Oklahoma sued, alleging the flow of weed through their states was facilitated by legal marijuana sales in Colorado. The lawsuit was dismissed by the U.S. Supreme Court in March.

Whether Nevada will see a similar issue arise with home-grows is uncertain. Nevada doesn’t have the same “caretaker” law that has helped fuel the black and gray markets in Colorado.

POLICING POT

Much like the current Nevada campaign, marijuana supporters in Colorado pushed the idea that legalizing the drug would result in fewer people going to jail or prison for possession. And after initial returns, they were right.

Marijuana possession arrests in Colorado plummeted after legalization, dropping by 47 percent from 2012 to 2014, according to the Department of Public Safety. The state’s law allows for possession of less than 1 ounce of pot.

Meanwhile, court filings related to weed — mostly citations that can add up to big fines, bench warrants and often jail time — dropped by 81 percent in that same time.

“I think the real reason to talk about (legalizing marijuana) is for criminal justice reasons,” said Colorado’s Director of Marijuana Coordination Andrew Freedman. “It’s been heartening to see those numbers go down.”

While growing and possessing pot are legal in Colorado, any form of public consumption remains illegal.

But that hasn’t stopped plenty of people from doing just that.

Anyone who takes a walk down the 16th Street Mall in downtown Denver — a mile-long, open-air pedestrian mall — won’t have to look, or sniff, for long before stumbling upon someone using marijuana. The parks, especially those near downtown, are notorious for public pot use.

Denver police cited about 760 people for using marijuana in public in both 2014 and 2015, the first years the city tracked that data.

Gerhardt said some of those cited are residents or tourists who are simply ignorant of the law. But others know full well that it’s not allowed, he said.

“There are a lot of those people who do it in open defiance of the law,” Gerhardt said.

Dan Rowland, a city spokesman speaking on behalf of the Denver Police Department, said police are actively enforcing the consumption law, but noted that it’s not the highest priority for police.

“Its obviously something that they’re aware of and keeping an eye out for,” Rowland said. “But it’s not something where our police are doing big, coordinated operations the way they would enforce more dangerous crimes that affect public health and safety.”

DRIVING WHILE STONED

One of Nevadans’ biggest concerns about legalizing marijuana involves driving while stoned. Opponents say the drug’s increased availability would cause more people to drive high and make the roads more dangerous.

So far in Colorado, the picture is mixed: Total DUIs have declined since the start of 2014, but marijuana-related DUIs make up a slightly larger share.

Colorado State Police issued 18 percent fewer citations for DUIs in 2015 (4,546) than 2014 (5,546), according to department data.

Alcohol-related DUIs made up the vast majority both years, but the share of pot-related DUIs rose from 12.2 percent in 2014 to 14.6 percent in 2015.

And this year, marijuana DUIs are trending at a much higher rate, accounting for about one-quarter of all DUI citations in 2016, according to State Police Sgt. Rob Madden.

But Madden said he doesn’t think people are driving stoned more often. Instead, he said state police officers are better trained to spot marijuana impairment in drivers.

Madden said troopers have learned more advanced detection techniques, such as looking at breathing patterns and skin conditions.

“They’re missing less,” he said.

POT’S TOURISM IMPACT

Then there is the potential impact on tourism, Nevada’s biggest industry. Could legal pot turn away a significant number of the more than 42 million visitors who came to the Las Vegas Valley in 2015?

Visit Denver, the local government’s marketing arm, put together a scathing report in December 2015 after receiving several complaints from convention planners about the conditions in the downtown area.

Most of the complaints referred to the visible homeless population, public marijuana use and overall conditions at the 16th Street Mall.

In emails to Visit Denver, planners called the area “dirty,” “smelly” and “depressing,” and said they were taking their conventions elsewhere.

Read more about it on the Review-Journal here: http://bit.ly/2dbwrIG