By Curtis Skinner
SAN FRANCISCO (Reuters) - Thousands of marijuana enthusiasts gathered on "Hippie Hill" in San Francisco's Golden Gate Park on Wednesday to light up joints, pipes and bongs in celebration of the annual but informal cannabis holiday, named 4/20.
The long-running Bay Area tradition, which authorities closely monitor but allow, could mark the last such observance while recreational marijuana remains illegal under state law in California.
Voters will decide in November whether to approve a ballot measure that would legalize adult possession and use of the drug for the purpose of just getting high.
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 day.
"It's pretty chill," said Erik Elder, 19, a college student who traveled from Sacramento with friends. "It's all lit. It's all just good vibes."
As the clock struck 4:20 p.m., cheers and clouds of smoke rose into the air.
"It's an appreciation of weed, and everyone coming together and enjoying the same thing," said 19-year-old barista Heidi Rice.
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. California is one of several states where advocates are pushing to follow suit.
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.
Marijuana magazine High Times has written that 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 drug.
San Francisco Supervisor London Breed coordinated with municipal agencies to handle traffic, litter and public safety issues surrounding the city's 4/20 event.
Several streets around the area were closed off, public buses were rerouted, and police increased their presence at the park with both uniformed and plain-clothes officers.
The event will cost the city between $80,000 to $100,000, according to Breed's aide, Samantha Roxas. Most of the money goes to cleanup afterward. Last year, some 5 tons of litter were left behind, she said.
(Reporting by Curtis Skinner in San Francisco; Editing by Sara Catania and Andrew Hay)