Voters in both Western states approved ballot initiatives in 2012 allowing personal possession and use of marijuana by anyone aged 21 and or older for purposes of just getting high, though public consumption of pot remains illegal.
In January the world's first state-licensed retail marijuana outlets opened for business in Colorado, and stores in Washington are set to follow suit later this year. Both states are among 20 that have already removed criminal sanctions for medical use of marijuana.
The federal government still classifies marijuana as an illegal narcotic, but the Obama administration has given states new leeway to experiment with legalized cannabis.
In Denver's Civic Center Park near the state capitol, revelers on Sunday gathered to hear music and listened to speakers during a weekend event that organizers billed as the "world's largest 4/20 rally."
The date of April 20, or 4/20, corresponds to the numerical code widely recognized within the cannabis subculture as a symbol for all things marijuana.
Police officers standing by on the fringes of the Denver festival issued 63 citations on Sunday, most for smoking pot in public -- a ticket that carries a fine of $150. About half as many were cited on Saturday, police said.
At least eight individuals were taken to a detoxification facility for treatment during the two days, police said.
Denver police spokesman Sonny Jackson said officers have refrained from wading into the crowd to arrest violators, but instead were citing people who openly defied the public consumption ban.
