Colorado has a shortage of cannabis after a sales spree in which about 100,000 people have bought the drug since it was legalised last week.
The supply shortages came as the Rocky Mountain ski resort of Aspen, a favourite with celebrities and billionaires, approved a licence for its first cannabis shop.
Its owner, cannabis entrepreneur Jordan Lewis, told the Aspen Times: "Hopefully we're going to create the finest marijuana establishment in the country."
On New Year's Day, Colorado became the first American state to allow legal sales of cannabis for recreational use. The three dozen shops licensed to sell the drug to anyone over the age of 21 have rung up about US$5 million ($6 million) in sales, including US$1 million on New Year's Day alone.
A sign at The Clinic, a cannabis shop in Denver, read: "We are currently out of recreational cannabis. Please check back tomorrow. Sorry for the inconvenience."
The shop's general manager, Ryan Cook, told local television: "We ultimately ran out of our flower products for retail sales. We had a thousand people in line every day for the first four days."
Other shops in Denver reported running out of cannabis-infused products such as chocolates and cakes, and some are rationing sales.
Nick Brown, of High Country Healing, told the Denver Post: "None of us could really prepare for what was going to hit us."