Thousands turned out at Golden Gate Park Friday to mark the unofficial celebration of pot.
People were openly rolling joints and taking puffs from bongs all afternoon. There was also plenty of edible pot to go around and a big smoke out at exactly 4:20 p.m.
"We all have our medical 215 cards and it's all legal and we're just doing our medication here, having a lovely day," medical marijuana user Andy George said.
Other advocates for medical marijuana converged on Oakland's federal building to protest a raid on the city's cannabis college.
Dozens of people held up signs condemning the crackdown that shutdown Oaksterdam University almost three weeks ago.
They also lit up joints to openly protest the Obama administration's stance against the drug. They want the federal government to respect California's medical marijuana law.
The origin of the term 4-20 is still up for debate, but many say it started at San Rafael High School.
It is so widely used that a California bill to regulate the use of medical marijuana was named SB420.