As marijuana use wafts its way toward Obama-era respectability, I can’t help recalling the pot scene in the Arlington of my youth.

For details of my own experimentation, you must visit a password-protected Website with a hefty subscriber fee (kidding).

But anyone around North Arlington circa 1970 could not have missed the flagrantly spray-painted graffiti that for years stained the underpass at Yorktown Boulevard and North Glebe Road: “Bill Welebir equals narc.”

That unsigned cry-out capturing the period’s underground youth drama, it turned out, was accurate – as I learned from a relatively recent online “confession.”

Recreational weed, as remembered by anyone who in the ’60s listened to “Puff the Magic Dragon” (kidding again), circulated discreetly among high school kids who peer-pressured pals at parties to pass the pipe around.

Arlington police and their D.C. counterparts began keeping tabs. William Wardell Welebir, the 19-year-old son of an Arlington physician working at a department store, in 1970 began offering law enforcement information on drug use in schools, in homes, even a commune, according to a 1972 Washington Post account by current Post education columnist Jay Mathews. Welebir acted because he wanted to become a police officer, he later said.

Suddenly the name Welebir was splashed on nearly a dozen walls, trestles and fences from D.C. to Chain Bridge to McLean to Sycamore Street.

Soon Welebir was receiving threatening phone calls and getting in fights with teenagers to whom he had boasted of his undercover work. The home he shared with his mother was firebombed – twice.

It was a strange sign of the power of anonymous graffiti. (I don’t recall that any of my friends who discussed Welebir did much independent fact-checking.)

So Welebir fled to Harrisonburg, for nine months, returning in 1972 to pose with his long hair for a news photographer in front of the immortal graffiti. But he had trouble finding a job in Arlington, and the police were soon regretting they relied on an inexperienced youth to report on his peers.

Flash forward to June 2009. In the online magazine DCWatch appeared a dispatch from Welebir, who’d migrated to Front Royal and South Carolina, in which he thanked police.

“Back in the late 1960s and early 1970s, I worked for detectives out of what was then the 3rd District Headquarters vice unit, on 23rd and M Streets, I think,” Welebir wrote. “Well, I’m old and terminally ill now and thinking back on the best times I had back then. They were going out and beating the streets of Georgetown and Northwest in search of marijuana and other illegal substances. Naturally, it was nothing like it has become over the years. We didn’t have to worry about guns and big money, just about cleaning up the streets.”

In 2010, Welebir was sentenced to five years in prison for burning down a Strasburg biker bar.

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Ex-Posties converge on Arlington: Longtime Washington Post Chairman Donald Graham, having sold off the newspaper, is moving his renamed company Graham Holdings to Arlington. That Rosslyn neighborhood is down the street from the onetime Courthouse home of the paper’s Web staff before it was united with the mainstream team downtown. Interestingly, Graham’s longtime chief executive officer at The Post, Boisfeuillet Jones, has also left the district for a commute to Arlington. He’s chief executive of the “PBS NewsHour” in Shirlington.