Throngs of people braved the wintry weather to make the historic purchases at 24 stores throughout the state, mostly in Denver.
In the photo above, Sean Azzariti, a former Marine and Iraq war veteran who suffers from post-traumatic stress disorder, completes the first legal marijuana transaction at 3D Cannabis Center in Denver.
Adam Hartle smiles and flashes a thumbs-up after completing a purchase at 3D Cannabis Center.
A customer surveys the products at a dispensary.
A customer at Northern Lights Cannabis Company.
Employees assist customers at Medicine Man retail store in Denver.
Store owner Toni Fox greets customers at 3D Cannabis Center.
An employee at 3D Cannabis Center stocks shelves.
A line forms for the 8 a.m. opening of the Cannabis Club in Breckenridge, Colo.
A long line curls around a store in Pueblo West, Colo.
A customer displays a receipt following a purchase at 3D Cannabis Center.
All photos courtesy of the Associated Press.