Is Code 4/20, Weed Day in Califonia

The Legend of the Waldos is the theory that explains it all, According to Chris Conrad, curator of the Oaksterdam Cannabis Museum in Oakland, California, 420 started as a secret code among high schoolers in the early 1970s.

A group of friends at San Rafael High School in Marin County, California, who called themselves "the Waldos," would often meet at 4:20 p.m. to get high.

For them, it was an ideal time: They were out of school but their parents still weren't home, giving them a window of unsupervised freedom. They met at that time every day near a statue of Louis Pasteur, the scientist who pioneered pasteurization. MORE on CNN