A brother of one of the Waldos was a close friend of Grateful Dead bassist Phil Lesh, as Lesh once confirmed in an interview with the Huffington Post. The Waldos began hanging out in the band's circle, and the slang spread.
Fast-forward to the early 1990s: Steve Bloom, a reporter for the cannabis magazine High Times, was at a Dead show when he was handed a flier urging people to "meet at 4:20 on 4/20 for 420-ing in Marin County at the Bolinas Ridge sunset spot on Mt. Tamalpais." High Times published it.
"It's a phenomenon," said one of the Waldos, Steve Capper, now 62 and a chief executive at a payroll financing company in San Francisco. "Most things die within a couple years, but this just goes on and on. It's not like someday somebody's going to say, 'OK, Cannabis New Year's is on June 23rd now.'"
Bloom, now the editor in chief of Freedom Leaf Magazine, notes that while the Waldos came up with the term, the people who made the flier — and effectively turned 4/20 into a holiday — remain unknown.