With the Colorado state capitol building visible in the background, partygoers dance to live music and smoke pot on the first of two days at the annual 4/20 marijuana festival in Denver on April 19, 2014. The annual event is the first 420 marijuana celebration since retail marijuana stores began selling in January 2014.

Brennan Linsley / AP

With the Colorado state capitol building visible in the background, partygoers dance to live music and smoke pot on the first of two days at the annual 4/20 marijuana festival in Denver on April 19, 2014. The annual event is the first 420 marijuana celebration since retail marijuana stores began selling in January 2014.