PHOTOS: 4/20 celebration on San Francisco's Hippie Hill

SAN FRANCISCO (KGO) -- Thousands are lighting up on Hippie Hill for San Francisco's 4/20 celebration on Friday, one of the world's largest celebrations of cannabis.

MAP: Where is weed legal?

Where is cannabis legal? Here's a map showing where legalization started and where it went from there.

Click here for more stories, photos, and video on cannabis.