On April 20, why is 420 slang for marijuana? Origin of 4/20

420 History: How April 20 Became Known as 'Weed Day

These stoner dads claim to have invented the 4/20 holiday

The Real Story Behind Why “4/20” Became a Stoner Holiday – Mother Jones

High holiday: 4/20 traces roots to these high school stoners - WHYY

What Is 4/20? A Brief History and How To Celebrate

What Is 4/20? - StayHipp

The origin of 4/20 Weed Day

Why Is Marijuana Called 420?

What is 420? The meaning behind the day and how it started

4/20 reminders: State urges marijuana users to consume safely

The History of 420