How Did '4/20' Become a Holiday for Weed?.
One common theory is that it stems from a California criminal code for those who distribute the drug.
According to CNN, California's 420 code is actually for obstructing entry on public land.
The state's medical marijuana program was created from a bill with the number 420.
Oaksterdam Cannabis Museum's Chris Conrad says "4/20" started as a code in Marin County, California, at San Rafael High School.
In the 1970s, a group called "The Waldos" would get together at 4:20 PM to smoke pot.
The time of the day was convenient as it was right after school ended with no parental supervision just yet.
"4/20" became a code word that allowed them to notify each other in front of unsuspecting parents.
From there, the phrase likely spread across the country
