four-twenty / 420

18 February 2026

There are many origin stories for 420, a slang term referring to marijuana, but unlike most slang terms, researchers have been able to pin down its actual origin with specificity. 420 was first used by a group of students at San Rafael High School in 1971, and it refers to the time of day, 4:20 pm, when they would meet to smoke pot and go off search for a mythical crop of marijuana plants.

San Rafael is in Marin County, on the other side of the Golden Gate Bridge from San Francisco, and in 1971 a group of students who called themselves the Waldos—because they used to congregate along a wall near the high school—got wind of a crop of pot plants allegedly growing near Point Reyes, further north. They would meet each day at 4:20 pm, after the school’s athletic practice, and venture north in search of the cannabis cache. They never found the pot, but in the course of their quest they smoked a lot of weed, had a lot of fun, and began using the term 420.

Marin County in the 1970s was also the stamping grounds of the Grateful Dead, and members of the Waldos had friends and family members associated with the band. 420 was picked up and used by Deadheads, as fans of the band call themselves, and from there the slang term spread to the wider world.

There is testimonial evidence that 420 was in use by the Waldos in 1971, but the first known use in print is from the “Question Man” column in the Red & White, San Rafael High School’s newspaper from 7 June 1974. The question reads:

If you had the opportunity to say anything in front of the graduating class, what would you say?

And the response from Question Man is “420.”

A 23 September 1975 letter from Dave Reddix to fellow Waldo Steve Capper, reads, in part:

My brother is Phil Lesh’s manager and last weekend I had a job as a doorman (backstage) at a concert. I smoked out with David Crosby and lesh [sic], got paid 20 bucks. I was laid off about three weeks ago Im [sic] collecting un-employment or “funenjoyment” that’s what it really is.

[…]

P.S. a little 420 enclosed for your weekend

The 420 in the letter is a reference to a joint that was enclosed.

420 got a big boost in May 1991 when the magazine High Times printed the text of a flyer that had been handed out at a Grateful Dead New Year’s concert. The flyer, however, gave a false origin for the term, that of 420 being a police code, one of many myths about the term that were to come. The flyer read:

Four-twenty started in San Rafael, CA in the late ’70s. It started as the police code for Marijuana Smoking in Progress. After local heads heard of the police call, they started using the expression “420” when referring to the herb—“Let’s go 420, dude!” After a while, something magical started to happen. People began getting stoned at 4:20 am and/or pm. There’s something fantastic about getting ripped at 4:20, when you know your brothers and sisters all over the country and even the planet are lighting up and tokin’ up right along with you. Now, there’s something even more grand than getting baked at 4:20. We’re talking about the day of celebration, the real time to get high, the grand master of holidays: 4/20, or April 20th. This is when you must get the day off work or school. We are going to meet at 4:20 on 4/20 for 420-ing in Marin County at the Bolinas Ridge sunset spot on Mt. Tamalpias [sic]. Just go to downtown Mill Valley, find a stoner and ask where Bolinas Ridge is. If you make it to Marin, you will definitely find it.

HELPFUL HINTS: Take extra care that nothing is going to go wrong within that minute. No heavy winds, no cops, no messed-up lighters. Get together with your friends and smoke pot hardcore.

After this was published in High Times, the term started to be widely used outside of Marin County and Deadheads.

Among the other false explanations that have been proposed over the years are:

• It was a section of [insert state here]’s penal code referring to marijuana
• It is the number of chemical compounds in marijuana
• It was the date [insert name of famous rock musician here] died
• It refers to Hitler’s birthday (Hitler was indeed born on 20 April, but the association with pot is never adequately explained).

And there are many other explanations. All without any evidence.

Sources:

Green’s Dictionary of Slang, accessed 17 January 2026, s.v. four-twenty, n., four-twenty, v.

Grim, Ryan. “Here’s the Real Story of Why We Celebrate 4/20.” Huffpost, 20 April 2016.

Mikkelson, Barbara. “The Origins of 420.” Snopes.com, 20 April 2023.

Oxford English Dictionary Online, March 2017, s.v. 420, n.

Reddix, Dave. Letter to Steve Capper, 23 September 1975. 420Waldos.com.

“Wake ’n’ Bake!” High Times, May 1991, 20.

Zinko, Carolyn. “Heads of the Class: The High School Kids Who Created 420.” San Francisco Chronicle, 20 April 2019, A1, A8. Newsbank: Access World News.

Image credit: Patty, 1970s. 420Waldos.com. Fair use of a copyrighted image to illustrate the topic under discussion.