SAN FRANCISCO (Reuters) - Thousands of marijuana enthusiasts who joined a massive smokeout on "Hippie Hill" in San Francisco's Golden Gate Park to celebrate the informal pot holiday named 4/20 left behind 11 tons of trash, officials said on Thursday.
About three dozen staff worked into Wednesday night after the event and were back out at the park cleaning up on Thursday morning after the event, San Francisco Recreation and Parks Department spokesman Joey Kahn said.
The date of April 20, or 4/20, corresponds with the numerical figure widely recognized within the cannabis subculture as a symbol for all things marijuana.
According to the marijuana magazine High Times, the concept of 4/20 originated in the early 1970s, as a group of teenagers in the Bay Area city of San Rafael used it as code to gather after school and smoke the plant.
Some 5,000 more pounds of trash were left this year compared to last year's event, he said. Kahn said he expected the costs to the department for the event to reach around $50,000.
The San Francisco Police Department, who were out in force both with uniformed and plain clothes officers, recorded eight arrests at the event and doled out 35 traffic-related citations.
The long-running Bay Area tradition, which authorities closely monitor, could mark the last such observance while recreational marijuana remains illegal under state law in California. Medical marijuana is legal in the state with a doctor's recommendation.
Voters will likely decide in November whether to approve a ballot measure that would legalize adult possession for recreational purposes.
The distinct odor of marijuana smoke mixed with the smell of barbecue in a gentle breeze wafting over an estimated 15,000 attendees enjoying the sunny Wednesday afternoon.
Marijuana, once widely demonized in the United States, has seen growing acceptance in recent years, especially among younger, more liberal Americans.
Although cannabis remains classified as an illegal narcotic under federal law, two dozen U.S. states have approved marijuana for medical purposes since California became the first to do so in 1996.
Since 2012 recreational use of the drug has been legalized in Colorado, Washington state, Oregon, Alaska and the District of Columbia.
Reporting by Curtis Skinner in San Francisco; Editing by Sharon Bernstein