The word · written by opus-5.5,
“420”, said four-twenty, is the best-known piece of cannabis slang in the world. It began as the meeting time of five schoolboys in a Californian town in 1971. Within thirty years it had become a code for smoking, a time of day, a date in the calendar, and a number that American officials have learned to avoid.
The Waldos
In 1971 five pupils of San Rafael High School, north of San Francisco, heard of a cannabis crop that its grower had abandoned. They had a map. They agreed to meet after school to look for it, at 4:20 in the afternoon, by the statue of Louis Pasteur in the school grounds, and they called the plan “4:20 Louis”.
They called themselves the Waldos, because they used to gather at a wall outside the school. Their names were Steve Capper, Dave Reddix, Jeffrey Noel, Larry Schwartz and Mark Gravich. They searched several times and never found the crop. “4:20 Louis” was shortened to “4:20”, and it stayed in their talk as a private word for smoking.
How it spread
One of the Waldos, Dave Reddix, later worked as a roadie for Phil Lesh, the bass player of the Grateful Dead. The band’s travelling followers picked the phrase up and carried it round the country.
The magazine High Times put it in print.
| Year | What happened |
|---|---|
| 1971 | The Waldos coin “4:20 Louis” |
| May 1991 | High Times first mentions 4:20 smoking and a 4/20 holiday, wrongly explaining the number as a police code |
| December 1998 | The magazine traces it to the Waldos. Its editor Steven Hager calls for 4:20 p.m. to be the accepted time of day to smoke |
Other explanations circulated for years, the police code among them, and none holds up. Another group from San Rafael, led by Brad Bann, claims to have used the term before the Waldos.
A date
Read as a date in the American way, 4/20 is 20 April, and that day has become the yearly gathering of cannabis users: in the words of one organiser, “half celebration and half call to action”. The usual form is civil disobedience: a crowd in a public place lighting up together at 4:20 in the afternoon.
In North America the regular sites include Hippie Hill in San Francisco’s Golden Gate Park, Civic Center Park in Denver, the Boston Common, Parliament Hill in Ottawa and the Vancouver Art Gallery. In Britain the crowd goes to Hyde Park.
Elsewhere the date has carried more risk.
| Country | 20 April |
|---|---|
| Taiwan | The first rally was held outside the legislature in 2019 and became annual |
| Mexico | Plantón 420, a protest camp and open cannabis garden beside the Senate, stood for three years until 2023 |
| Hungary | In 2025 police tried to ban the Budapest gathering under a new constitutional clause against “promoting” drugs. The supreme court let it go ahead |
| Northern Cyprus | A first event was held in 2015, in a territory known for strict drug laws |
A number officials notice
The number has leaked into public life. California’s law of 2003 regulating medical cannabis was Senate Bill 420. A bill in the United States Congress to regulate cannabis like alcohol was numbered H.R. 420 in 2019.
It has also become a nuisance. Road signs for mile 420 were stolen so often that Colorado replaced the one on Interstate 70 with a sign reading 419.99, and Idaho put up 419.9. The American government and some cities run “anti-420” campaigns each April.
Businesses use it as a wink: restaurant chains run 20 April promotions, and Elon Musk bought Twitter in 2022 at 54.20 dollars a share, with the papers signed on 20 April.[1][2][3]