The U.S. Congress passes the Marihuana Tax Act making it illegal to possess or transfer cannabis, except for medical or industrial uses, which were subject to an excise tax.
The National Institute of Drug Abuse partners with the University of Mississippi to grow marijuana for research purposes, a program that still exists.
Congress passes the U.S. Controlled Substances Act, part of the Comprehensive Drug Abuse Prevention and Control Act, which replaces the Marihuana Tax Act and classifies marijuana as a Schedule 1 controlled substance.
The Colorado General Assembly decreases the penalty for possessing an ounce or less of marijuana.
The U.S. government creates the Investigational New Drug compassionate access research program, which allows some patients to receive marijuana for medical purposes. The program was shut down in 1992.
California becomes the first state to allow the use of marijuana for medical purposes when nearly 56 percent of voters approve Proposition 215.
Former Colorado Secretary of State Vikki Buckley doesn’t count votes from Amendment 19, a marijuana legalization measure, because she says proponents didn’t collect enough signatures to put it on the ballot.
Colorado voters approve Amendment 20, making the medical use of marijuana legal for patients with certain conditions and a recommendation from a doctor. Nearly 54 percent of voters approve the measure.
The Colorado Department of Health and Environment creates the Medical Marijuana Registry, which issues cards to patients approved to use medical marijuana.
The Colorado Board of Health limits to five the number of patients a medical marijuana caregiver can have.
With 54 percent of the vote, Denver residents approve a measure making it legal for adults to possess as much as 1 ounce of marijuana.
Colorado voters reject a ballot initiative that would have allowed adults to possess as much as 1 ounce of marijuana.
A Denver district judge rules that the state Board of Health’s rule allowing a medical marijuana caregiver to provide for only five patients didn’t include public input, thus allowing caregivers to provide for more than five patients.
The Obama administration announces a policy change to end raids on medical marijuana dispensaries.
The Colorado Board of Health considers reinstating the rule allowing caregivers to provide for only five patients but opts not to impose a limit.
The U.S. Department of Justice issues a memo to federal prosecutors instructing them not to use federal resources to prosecute people who are complying with state medical marijuana laws.
With 71 percent of the vote, residents of Breckenridge approve a ballot measure that allows adults to possess as much as 1 ounce of marijuana.
With more than 54 percent of the vote, Nederland residents approve a measure removing all criminal penalties against buying, possessing, growing, consuming, selling or transporting marijuana for anyone 21 or older.
Colorado legislators approve Senate Bill 109 to regulate the medical side of the medical marijuana industry. They also approve House Bill 1284, which regulates the business side of the industry.
Colorado Gov. Bill Ritter signs Senate Bill 109 and House Bill 1284 into law.
July 1, 2010
Colorado’s new medical marijuana laws take effect.
Aug. 1, 2010
By its application deadline, the Colorado Department of Revenue receives applications from 309 infused-product makers, 809 medical marijuana centers and 1,219 growers, collecting more than $8 million in fees to operate the medical marijuana program.
Aug. 27, 2010
The Colorado Department of Revenue releases 92 pages of draft rules after the first meeting of a workgroup of medical marijuana stakeholders to help create rules to regulate the industry.
Sept. 1, 2010
Colorado’s medical marijuana centers are required to certify that they grow 70 percent of the marijuana they sell.