420 is associated with weed because a group of high school friends in California in the early 1970s used “420” as a secret code for meeting up to smoke cannabis, and that in‑joke slowly spread into global stoner culture through the Grateful Dead and cannabis magazines.

Why is 420 associated with weed?

Quick Scoop

The short version

  • In 1971, five students at San Rafael High School in Marin County, California, used “420” as a codeword for smoking weed and meeting at 4:20 p.m.
  • They were nicknamed the “Waldos” because they used to hang out by a wall at school.
  • The term traveled into the Grateful Dead scene, then into cannabis media like High Times, and eventually became worldwide slang for cannabis and an unofficial weed “holiday” on April 20 (4/20).

The origin story: The Waldos at 4:20 p.m.

Think early 1970s, Northern California, after school.

  • Five friends at San Rafael High School (Steve Capper, Dave Reddix, Jeffrey Noel, Larry Schwartz, and Mark Gravich) made plans to go search for an abandoned cannabis grow and would meet at 4:20 p.m. by a statue on campus.
  • 4:20 p.m. worked because classes and most extracurriculars were over by then, so it was a low‑profile time to hang out and smoke.
  • They started saying “420” to each other as shorthand for “let’s go smoke” or “weed time,” turning a clock time into a secret code.

Over time, “420” stopped being just their private joke and became a little piece of local stoner slang.

From inside joke to global code

How does a tiny high‑school code become a worldwide cannabis symbol?

  • One of the Waldos later had connections to the band the Grateful Dead, working around the group and its circle.
  • The Dead’s fanbase (Deadheads) were deeply embedded in 1970s–80s counterculture, so slang and in‑jokes spread quickly in that scene.
  • In 1990, Deadheads in Oakland circulated a flyer inviting people to smoke “420” on April 20 at 4:20 p.m.; a copy reached a cannabis reporter, who helped popularize the term in High Times magazine.

Once a big cannabis magazine and a major touring band used it, “420” evolved into a universal nod for cannabis and a specific time/date to celebrate.

Myths about “420” (and why they’re wrong)

Over the years, a bunch of alternative explanations have floated around. Common myths:

  • It’s a police radio code for “marijuana in progress.”
  • It’s the number of active chemicals in cannabis.
  • It’s tied to Adolf Hitler’s birthday (also 4/20) or Bob Marley.
  • It’s a reference to a Bob Dylan song where 12 × 35 = 420.

Mainstream historical reporting and cannabis historians say these are just myths; police codes and chemical counts don’t line up, and there’s no real evidence linking “420” to those stories.

Instead, multiple independent outlets trace the most credible origin back to the Waldos’ 4:20 p.m. meetups in Marin County.

What 420 means today

“420” has grown way beyond a secret meeting time.

  • It’s general slang for weed or getting high (“He’s 420‑friendly”).
  • 4:20 p.m. is treated as a “perfect time” to smoke among fans.
  • April 20 (4/20) has become an unofficial global cannabis holiday, with public gatherings, concerts, and dispensary promotions in places where weed is legal.
  • As legalization expands, some see 4/20 as a symbol of cannabis activism, community, and normalizing responsible use, not just an excuse to get stoned.

Bottom line: 420 started as a quiet after‑school code between a few teenagers and evolved into one of the most recognizable numbers in modern cannabis culture.

TL;DR: 420 is associated with weed because a small group of California high‑school students used “420” for their 4:20 p.m. smoke sessions, the term leaked into the Grateful Dead scene, got amplified by cannabis media, and eventually turned into a worldwide shorthand for cannabis and the April 20 weed “holiday.”

Information gathered from public forums or data available on the internet and portrayed here.