It happened in Canada: This series on the revolutionaries, luminaries and criminals who have visited the Great White North, was originally published in 2014

At a London, Ont., hockey rink packed with as many as 7,000 stunned Canadians, Johnny Cash had just cemented the most storied romance in country music history.

And according to Cash bassist Marshall Grant, it had all been a terrible, drug-fueled mistake.

“When he proposed to her on the stage in London, he was not straight,” Mr. Grant told a Cash biographer soon after the singer’s 2003 death.

Mr. Cash and June Carter had just finished their duet of Jackson — the recording of which would soon earn them a Grammy — before Mr. Cash fixed his gaze on his singing partner and blurted out “June, will you marry me?”

“When we walked off the stage … there in that old ice hockey arena, I said ‘June, you’ve made a mistake … if you go through with it, you are in for one hell of a life,” said Mr. Grant.

Although the London audience had seen a playful, energetic Mr. Cash on stage at the London Ice House that February, 1968, the musician had only just emerged — with Ms. Carter’s help — from the worst of years of alcoholism and prescription drug addiction.

In his most storied low point, only months before the London concert, Mr. Cash claimed to have climbed into a Tennessee cave intending to kill himself. As the Cash legend goes, his years of addiction were helped along by his unrequited love of June Carter, an established musician in her own right who had spent years as Mr. Cash’s touring partner.

The attraction was certainly not one-sided. According to Mr. Cash’s first wife, Vivian, Ms. Carter had once cornered her with the declaration “he will be mine.” And, of course, it was Ms. Carter who penned the lyrics to Ring of Fire, Mr. Cash’s hit about being consumed by the roaring flames of “wild desire.”

London’s proposal was not the first time Mr. Cash had pitched marriage to June Carter, but this was the first time since his divorce had been finalized.

The rest of the Carter family were onstage that night in London; June’s mother Maybelle and her sisters Anita and Helen. And all three of them quietly watched as the awkward scene playing out in front of them.

Ms. Carter initially tried frantically to brush off the invitation. She shot back “sing a song, John” and tried to lead the band into the next number on the setlist. But with Mr. Cash stoically awaiting an answer, and with cries of “say yes” coming from the audience, Ms. Carter quietly assented.

“They were all a dither for a moment or two, and I don’t think she answered him, or at least not so that we all could hear,” witness Ralph Willsey recounted in a story for the Ottawa Citizen in 1998.

Despite being an unabashed icon of Americana, Mr. Cash spent a surprising amount of his early career on a seemingly unending tour of Canadian venues. In one two-year period in the early 1960s, the tiny Ontario village of Lucan saw an incredible two visits by the singer.

Many Canadians can even credit their first use of an ATM to the Man in Black.

“How many times have you been caught short, and the only thing between you and your money is the clock … you know, Canada Trust has a better idea,” the musician told Canadian TV audiences in a 1985 commercial announcing the rollout of the bank’s new line of automatic “JohnnyCash” machines.

Most notably, in the heady days from 1960 to 1973, Mr. Cash’s manager was a Canadian; Saul Holiff, a former fruit vendor from London, Ont.

In 1961, it was Mr. Holiff who made the fateful decision to hire June Carter as a singing companion to the outlaw country pioneer. And in 1966, it was Mr. Holiff who discovered the singer near-death from a drug overdose after a performance in Toronto. “For all intents and purposes, he was dead,” the manager would say in an audio diary.

Post-Cash, Mr. Holiff got a history degree at the University of Victoria and died in Nanaimo, B.C., from suicide at the age of 80 in 2005. In 1998, he recalled the London proposal by telling the Ottawa Citizen: “I couldn’t honestly say I did hear it, but then what does anyone recall over that span of time unless it was stamped on your forehead?”

But in Mr. Holiff’s hometown, there remain hundreds of people — most of them now approaching retirement age — who vividly remember witnessing the bizarre spectacle of the Carter/Cash engagement. At the time, though, most figured they had been watching an act.

“Well, we really didn’t think it was for real,” resident Ruth Ann Bynen told a local TV station in 2006, when the Johnny Cash biopic Walk the Line renewed interest in the Canadian proposal (the movie identifies the city as “Ontario, Canada”).

“I don’t think you could fully understand how significant that proposal was until you saw how it, in retrospect, was the turning point in Johnny Cash’s life,” said Andy Oudman, a local radio personality, also in 2006.

In 1975, when Mr. Cash was in Toronto, CBC interviewer Elwood Glover gushed to the superstar that his relationship with Ms. Carter was “almost idyllic” and asked “what is the remarkable quality of your wife?”

“She and I still got a fantastic love affair going, so I’m not going to tell you all,” Mr. Cash replied.

The relationship was never as storybook as it seemed, however.

For starters, Mr. Cash had abandoned a wife and four children to be with June.

In an autobiography written just before her death, Mr. Cash’s first wife Vivian described seething whenever she saw the “glowing and happy” couple in televised interviews.

“I wished a big hook would come down and drag [June] off the stage each time she started in,” she wrote, describing June as having a “devil-driven” control over her ex-husband.

And, it was only months after their fateful Ontario concert date that Mr. Cash had a brief affair with June’s sister Anita, according to biographer Robert Hilburn.

Yet despite infidelities — and several drug relapses — the pair grew old together. Upon Ms. Carter’s death in 2003, the couple had just celebrated their 35th wedding anniversary.

As a Billboard magazine obituary put it, “their union was one of the strongest in the entertainment business.”

Yet Ms. Carter never seemed particularly enthralled by her husband’s unorthodox Canadian proposal.

“I got caught,” is how she justified her acceptance to Mr. Grant backstage. And for years afterwards she bristled at having to repeatedly recount the story to interviewers.

“I would have liked it if he’d gotten down on his knees and proposed to me,” she said in 1981.

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