UNIVERSITY PLACE (WASHINGTON) — Chambers Bay Golf Course had already served as the backdrop for one big event in the life of the 21-year-old Jordan Spieth (picture). A month after Spieth won his first pro event as a PGA Tour rookie, he was a witness at a wedding on the grounds between his caddie, Michael Greller, and the former Ellie Morris.

Two years later, it was Spieth’s turn to have a monumental moment all his own.

With a one-stroke victory over Dustin Johnson and Louis Oosthuizen on Sunday (yesterday morning, Singapore time) in the 115th United States Open, Spieth became the first male player since Gene Sarazen in 1922 to win multiple Majors before his 22nd birthday.

He is also the youngest winner of the US Open since Bob Jones in 1923. Spieth, the reigning Masters champion, is the sixth man to win the first two legs of the Grand Slam, and the first since Tiger Woods in 2002.

Spieth, whose birthday is in July, opened with a bogey but closed with two birdies on his last three holes for a one-under 69 and a 72-hole total of five under.

Playing in the group behind Spieth, Dustin Johnson three-putted from 12 feet for a par on 18 to finish with a 70.

He was tied for second with Oosthuizen, the 2010 British Open champion from South Africa, who played the final nine holes in a record-equaling six-under 29 for a 67.

“I’m still amazed that I won, let alone that we weren’t playing tomorrow,” Spieth told reporters. “So for that turnaround right there, to watch that happen, I feel for Dustin, but I haven’t been able to put anything in perspective yet.”

Adam Scott, the 2013 Masters champion, posted the low round of the day, a 64, to vault into a share of fourth at three under.

It was surreal for Scott to be chasing Spieth, who as a child ran down Scott for his autograph at the Byron Nelson tournament.

He displayed the signature on his bedroom bulletin board in his family’s home in Dallas. Spieth recently moved to his own home, but Scott’s autograph is still hanging in what is now a guest room in his parents’ home.

“He certainly is making me feel my age a little bit if someone’s got my autograph on the wall and he’s playing out here,” Scott said, adding: “I think he’s handled himself incredibly well. I hope he keeps doing the same.”

On a day when his putts were not all falling and his tee shots took some strange bounces, Spieth showed a patience and maturity that belied his youth. His mettle was tested in the stretch when he carded a double bogey at the par-3 17th to fall into a tie with Oosthuizen. Spieth rebounded with two perfect shots at No 18, playing as a par 5, to set up the birdie that sealed the win.

On his thoughts as he walked off the course at five under, Spieth said: “I didn’t think it was good enough. But man, I couldn’t be more happy right now.”

Cameron McCormick, who has worked with Spieth for nearly a decade, said Spieth’s ability to perform in the clutch could be traced to his “bulletproof self-image”. He added, “No matter what happened previously, he can will the outcome to his desire.”

With the tee boxes on multiple holes changing from day to day, drastically altering the players’ lines, an ability to adapt was a requisite for success this week. Spieth’s choice of attire on Sunday was a testament to his flexibility.

When he became a spokesman for Under Armour shortly after turning pro in 2012, Spieth was finicky about his wardrobe. He sent back bright-coloured pants, making clear he preferred blues and greys, and no white pants.

So what was Spieth wearing when he sealed his first Major victory at the Masters in April and again on Sunday when he tried to keep his calendar year Grand Slam hopes alive? White pants.

Rising from the site of an old sand and rock quarry in 2007, the Chambers Bay course is even younger than Spieth, and unlike the champion it spawned, it did not get high marks from the players, especially its dry, bumpy greens — Henrik Stenson called it “putting on broccoli”, Rory McIlroy felt it was more akin to “cauliflower”.

Assessing the Chambers Bay golf course, Geoff Ogilvy, the 2006 champion who closed with a 67, said: “You have to move the ball both ways and you have to use your brain, which is a rare thing in modern golf and something we’re not very good at, I don’t think. It’s going to be a class act of a player who wins, and really that’s all you want.” THE NEW YORK TIMES

275 Jordan Spieth (US) 68 67 71 69

276 Louis Oosthuizen (RSA) 77 66 66 67, Dustin Johnson (US) 65 71 70 70

277 Adam Scott (Aus) 70 71 72 64 Cameron Smith (Aus) 70 70 69 68 Branden Grace (RSA) 69 67 70 71

278 Charl Schwartzel (RS) 73 70 69 66

279 Brandt Snedeker (US) 69 72 70 68

280 Rory McIlroy (NIR) 72 72 70 66 Shane Lowry (Ire) 69 70 70 71 Jason Day (Aus) 68 70 68 74