Some would have considered it slow torture:

A small, windowless cubicle deep inside the National Archives in Washington, D.C.

A set of headphones.

And, reel after agonizing reel, hundreds of hours of then-President Richard Nixon planning his daughter’s wedding one minute and covering up a massive criminal conspiracy the next.

“It got tiring and there were (fellow archivists) who didn’t particularly enjoy it,” said Christopher Beam, now an adjunct professor of history at the University of Southern Maine. “I found it kind of fascinating.”

Forty years ago this Saturday, Nixon became the first U.S. president to resign his office. It was the final, climactic moment in a two-year saga that began with a break-in at the Democratic National Committee headquarters inside the Watergate office complex and ended with the release of the infamous “smoking gun” tape in which Nixon himself plots his own cover-up just six days after the clumsily executed crime.

Beam, sitting in that cubicle a few years later, heard it all. From the barely audible discussions of foreign policy to the mysterious 18½-minute gap that to this day has never been adequately explained, he spent four years as an archivist with the Nixon Presidential Materials Project, Tapes Section.

Meaning he made his living eavesdropping on history. And the more he listened – of the 3,700 total hours of recorded conversation, Beam personally archived about 1,500 hours – the more he learned.

Beam grew up in Brunswick, graduated from Williams College and enlisted in the Marines in 1967, at the height of the Vietnam War. He served in Vietnam from 1968-69 and, upon his discharge a year later, spent the next five years earning his Ph.D. in history from the University of Illinois at Urbana-Champaign.

Unable to find a teaching position, he landed an internship with the National Archives in 1977. That led to the post-Watergate tapes project and, for a 33-year-old budding historian, the opportunity of a lifetime.

The tapes, first revealed by presidential aide Alexander Butterfield in stunning testimony before the Senate Watergate Committee, were as rudimentary as they come. Slow-moving and paper thin (the archivists worked off more durable copies), they were labeled only by their date of recording before Beam and his colleagues, four years after Nixon left the White House, began listening in to every word.

His personal feelings toward Nixon before he strapped on the earphones?

“Let’s put it this way,” said Beam. “When I got back from Vietnam, I was strongly opposed to the war and I felt like the United States had made a terrible mistake getting involved in it. It was a lost cause. Nixon’s approach dragged out the war, so yes, I opposed Nixon.”

Still, the more he listened to the scratchy tapes, all the product of a “jury-rigged system” secretly installed by the Secret Service at Nixon’s order back in 1971, the more Beam came to appreciate the inner complexities – good and bad – of the nation’s 37th president.

“Clearly, he was a master politician,” Beam said. “I would say probably his biggest strength was that he was able to think strategically both in terms of politics and diplomacy. Of course, the tapes also reveal his shortcomings, including those shortcomings that eventually led to his downfall.”

First and foremost was Nixon’s utter naiveté at installing the voice-activated recorders in the first place – not only in the Oval Office, but also in his hideaway office in the Old Executive Office Building, his Cabinet room, the Lincoln Sitting Room, and for a brief time, even the Aspen Lodge at Camp David. Other presidents dating to Franklin D. Roosevelt had hit the record button from time to time, but this level of surveillance was unprecedented.

Some lay that to Nixon’s paranoia. But Beam saw – or heard – something more.

“I do believe Nixon’s basic motive for maintaining a taping system was historical; you’d have the best record of what went on in his administration,” Beam said.

Fair enough. But why in the world didn’t he hit the “off” button on that fateful morning with H.R. Haldeman? Or, nine months later, when then-White House counsel John Dean warned Nixon of “a cancer … close to the presidency” that was only growing worse by the day?

Suggests Beam: For all his political prowess, Nixon wasn’t a gadget kind of guy.

“Nixon never operated the system,” noted Beam. “He never signaled to anybody to turn it on. It was automatically operated. He was aware it was there, but I don’t think he understood how it operated and I think it sort of receded into the back of his mind.”

Amazing. We tell our kids these days to be careful what they post on Facebook, yet 40 years ago we had a president incriminating himself willy-nilly on a recording system he installed in the first place.

Which brings us to perhaps the most captivating portion of the tapes: The 18-plus minutes of silence during a conversation on July, 20, 1973, between Nixon and Haldeman. Longtime Nixon secretary Rose Mary Woods later took responsibility for recording over about five minutes of the gap, but Beam (who’s listened more than once to the entire, static-filled segment) still doesn’t buy it.

“I would agree with the federal district court because they investigated this. I believe for sure there was a deliberate erasure,” he said. “I can’t say for sure who did it, (but) I don’t believe Rose Mary Woods did it.”

Beam moved on to other projects in 1982 and finally left the National Archives in 1988. For the next 18 years, he lectured and directed the Edmund S. Muskie Archives at Bates College in Lewiston. (Ironically, Muskie was among those targeted by the Nixon re-election campaign’s “dirty tricks” operations around the same time of the Watergate caper.)

But even in semi-retirement – Beam still teaches part time at USM – he sees the Nixon tapes as a “unique and priceless” window to an era most of his students can only imagine. Reel-to-reel recorders? Magnetic audio tape? Who does that?

Richard Nixon did – and in the process, he changed the course of history.

Imagine if he’d had a smartphone.