With Dustin Johnson faltering on the final hole, Jordan Spieth emerged with the win at the U.S. Open, giving him his second major title of the year. (Paul Buck/European Pressphoto Agency)

The only thing standing between Dustin Johnson and one of the most miraculous and gutsy victories in the 115-year history of the U.S. Open was 12 feet 4 inches of some combination of fescue and poa annua grasses, an unknown quantity of sand and — just maybe — a couple of heads of cruciferous vegetables. This moonscape monstrosity called Chambers Bay, with its stricken greens and random bounces, may not have deserved it, but major championship golf has rarely produced a more dramatic ending than what was unfolding here.

And then the only thing standing between Johnson and an 18-hole playoff with Jordan Spieth on Monday was four feet of the same bumpy combination of elements. And then the only thing standing between Johnson and a brutal, soul-crushing loss was nothing. He had three-putted away the U.S. Open.

The champion of this U.S. Open is the same man who was crowned champion of the Masters two months earlier. It is Spieth, the 21-year-old phenom and Sunday stalwart, who held himself together under a crucible of pressure to shoot a closing round of 1-under-par 69 and earn a one-shot victory over Johnson (70) and a hard-charging Louis Oosthuizen (67) in one of the most memorable finishes in this tournament’s long history.

Having won the year’s first two majors, the first to do so since Tiger Woods in 2002, Spieth will head to St. Andrews in Scotland a month from now to attempt to snag the third leg of golf’s Grand Slam. The fourth major, the PGA Championship, is at Whistling Straits (Kohler, Wis.) in August. Spieth is the youngest golfer to own two major titles since Gene Sarazen in 1922 and the youngest U.S. Open champ since Bobby Jones in 1923.

Spieth, having just birdied the par-5 18th hole one group ahead, was in the scoring tent with his caddie as the drive-bombing Johnson — following a mammoth tee shot and a beautiful 5-iron to the green — looked over his 12-footer for eagle and the U.S. Open title.

A three-putt by Dustin Johnson from 12 feet away prevented him from the victory and allowed Jordan Spieth to take the U.S. Open. (Harry How/Getty Images)

Spieth, he would say later, was muttering to himself about the double-bogey at 17: “How did I possibly let this happen?” Caddie Michael Greller was reassuring him: “Dude, just be positive.” Moments later, after Johnson missed the four-foot comebacker that would have forced a playoff, Spieth and Greller stood there in silence, then hugged.

“I’m in shock. Wow,” Spieth stammered into Fox’s microphone when it was stuck in his face. “I was just hoping for a chance [in a playoff] tomorrow.”

A day of high drama, when Spieth and Johnson entered Sunday as part of a four-way tie for the lead and then traded blows for the better part of the afternoon in back-to-back pairings, reached its climax on the final two holes.

Spieth came to 17th green — just as Amtrak 509, the Cascades, went chugging past on its way from Seattle to Portland — with a three-shot lead and left there a few minutes later in a tie. While Spieth was uncharacteristically chopping his way around the 17th — tee shot in the right hay, impossible pitch to 40 feet and a three-putt for double-bogey — Oosthuizen, the 2010 British Open champ, was putting the finishing touches on an impossibly exquisite back-nine 29 with a birdie up ahead at 18 to get to the clubhouse at 4 under.

So Spieth had Oosthuizen closing in on him up ahead and Johnson, the quiet big-bomber, coming at him from behind. Playing in the day’s final pairing, Johnson rolled home an eight-footer for birdie at 17, moments after Spieth played his second shot to the par-5 18th. When Spieth two-putted for birdie at 18 to get to 5 under — clapping to acknowledge the boisterous gallery at the final green — he held a one-shot lead, with only Johnson in position to catch him.

Johnson, who turns 31 on Monday, was leading the entire tournament in putting entering the final round, but there is putting — and then there is putting on the 72nd hole of a major championship with the trophy on the line. Johnson’s first putt on 18, the 12-footer for eagle, was too strong, blowing through the break and rolling four feet past. And his second putt, the four-footer for birdie and a berth in a Monday playoff, was a straight-up yank job that never had a chance.

“I might have pulled [the birdie putt] a little bit. But still to me it looked like it bounced left. It’s tough. It’s very difficult,” Johnson said. “I did everything that I could. I tried my damnedest to get in the hole. I just couldn’t do it.”

It was the fourth brutal loss for Johnson in major championships, following the 2010 U.S. Open, when he carried a three-shot lead into Sunday but shot 82 and finished eighth; the 2010 PGA Championship, when he mistakenly grounded his wedge in a bunker at the final hole and incurred a two-shot penalty that kept him out of a playoff; and the 2011 British Open, when he fell out of contention on the back nine Sunday.

The quality of its eventual champion, the preternaturally poised Spieth, gave this tournament and this golf course a measure of legitimacy that many would argue it didn’t deserve.

A week of criticism of Chambers Bay — its greens likened to “broccoli” by Henrik Stenson for their inconsistency and to “cauliflower” by Rory McIlroy for their lack of green color — reached its climax Sunday, when golfers on their way to the airport let loose with all the frustration they had been holding in.

But for all of the criticism the course got, it wound up producing a dazzling leader board with a top 11 that included five players who already owned major titles (Spieth, Oosthuizen, Adam Scott, Charl Schwartzel and McIlroy) and two others, Johnson and Jason Day, considered among the best in the world who don’t. McIlroy, who reeled off six birdies in a 12-hole span to get to 2 under before petering out with bogeys on 15 and 17, was one of several players back in the pack who made spirited runs.

None was more remarkable than Oosthuizen’s. Four over par at the turn, he birdied five straight holes on the back nine, then tacked on another at 18 to post a 29 on the back nine and apply more than a little pressure to Spieth and Johnson. Meanwhile, South Africa’s Branden Grace hung around the lead and held a share of it as late as the 16th tee until an out-of-bounds tee shot and a double-bogey there sunk him.

Spieth didn’t appear to like Chambers Bay any more than anyone else on the premises this week, but better than anyone else in the field — at least those at the same elite level, admittedly a very select group — he managed to shrug off the indignities and miscarriages of justice that the course foisted upon them.

“Someone has to hold the trophy,” Spieth said. “. . . I didn’t think too much of the layout. [But] that’s what’s great about the U.S. Open — it’s a grind.”