It is now legal to buy marijuana for recreational purpose in Colorado.
At least two dozen pot shops opened in eight towns on Wednesday, with thousands of people flocking to buy the drug.
It is the world's first fully legal marijuana industry—No doctor's note required.
And despite freezing temperatures, hundreds of people stood in line Wednesday to test the nation's first legal recreational pot shops.
"I've been waiting 42 years for freedom," Danny Conners from Wisconsin said.
"I sold my house couple of months ago to prepare to move to Colorado," Jacob Elliot, daily marijuana user, said.
"We drove 17 hours to get here," Steven Reynolds admitted.
"We want to be the Costco of marijuana," a local pot seller proclaimed.
Legalization opponents fear that retail pot will endanger public health.
Counselors and physicians say addiction is a serious issue for many young people.
"Some people think that marijuana is just psychologically addictive, not physically addictive, it's just a soft drug, something like that," Dr. Christian Thurstone, the medical director of a teen substance treatment program at Denver Health and Hospital Authority, said.
"But I can tell you from personal experience that these kids who come to see us are dropping out of life," he continued.
Although legal sales are limited to adults over 21, many believe the drug will be more widely available to teens leading to greater illegal use.
Even though the new rules are underway in Colorado, authorities are warning buyers that bringing marijuana across state line is against federal law.
Colorado's retail experiment is crucial to determine whether marijuana can be sold like alcohol, or whether major modifications are needed.
Washington state has also legalized recreational pot, and will face the same restrictions when its retail shops start operation in late spring.