The state constitution was amended on November 6, 2012 by a vote of 55.3% to 44.7 which made possession of marijuana to be legal for personal use. The initiative for the bill started on 2011/2012 and was approved as sufficient on February 27 2012 to appear on the general ballot for the November election.
Colorado legalized marijuana with the passing of Amendment 64 on November 6, 2012. The ballot was an amendment the the state constitution, put up for vote from an initiative by the citizens of Colorado. It won with 55% of the people voting yes in favor of legalization. The ballet allowed adults 21 and over to posses up to 1 ounce of marijuana. It also allowed the state to regulate sales and taxes. Giving them control over growing, retail, and testing facilities. Retail sales opened to the public on January 1, 2014.
Between 1998 and 2000, Colorado citizens got initiatives on the ballot to legalize medical marijuana. In 2005 students from two different colleges got an initiate on the ballot and succeeded to legalize recreational marijuana use in the city of Denver, after two college students died from alcohol poisoning. In 2010 Colorado Legislature passes HB10-1284, which legalizes full-scale dispensaries, marijuana cultivation operations and manufacturers for marijuana edible products. On November 6th, 2012, Colorado became the first state in the world to vote in favor of ending marijuana prohibition with about 55% of the Colorado electorate voting in favor Amendment 64.