US Open gallery: Webb's win
What They Said: Tiger upbeat
Plays of the Day: Westwood's tree torment
American Webb Simpson won the 2012 US Open after Graeme McDowell narrowly missed a 20-foot birdie putt to tie at Olympic Club on Sunday.
Simpson, a two-time winner on the PGA Tour, set the clubhouse target at one-over after an impressive final round of 68, a score that overnight leaders McDowell and Jim Furyk had the chance to match as they reached the 18th in the final round.
Both men needed birdies to force an 18-hole play-off on Monday, but Furyk's chances died after he found the greenside bunker with his approach shot. McDowell, however, had a 20-footer to tie - but the Northern Irishman saw his attempt slide wide as 26-year-old Simpson claimed his maiden major title.
Simpson, who did not initially realise he had won as he watched McDowell's final roll of the dice fail, was overwhelmed at his breakthrough success.
"I couldn't be happier," Simpson said at the post-tournament presentation, which was briefly interrupted by an inebriated fan. "It was so nerve-wracking, I expected McDowell to hit the hole and have a chance.
"I got off to a slow start but I knew that there were some birdie chances on the back and luckily those chances came.
"I have never had nerves like this before - at times I had to hit my legs because I couldn't really feel them."
Victory for the American was secured around the turn, after an impressive run of putting that thrust him back into contention having fallen six shots behind the leaders at one point.
Starting three-over at the beginning of the day, Simpson was five-over by the fifth as he struggled to get to grips with the course setup. Around the turn, however, everything changed - Simpson made four birdies in five holes during a spell where he one-putted six greens in succession to also save a couple of crucial pars as he suddenly leapfrogged back into contention.
From there, it was a matter of staying calm under the pressure of contention as Simpson looked to close out his round. Yet, while everyone else struggled the North Carolina kept making birdie chances for himself - narrowly missing out with six good opportunities in a row between the 12th and 17th as he kept adding the pars.
Having reached the 18th still one-over for the tournament and in a share of the lead, disaster nearly struck as Simpson pushed a nervy approach shot into a horrible lie in the greenside rough. It was here that the American earned his victory, however, feathering a wondrous chip that caught the bank and rolled to five-feet - leaving what would prove to be a decisive putt that he fearlessly struck in.
It was Furyk and McDowell who had led for much of the day, with the American - winner of the tournament in 2003 - out on his own for much of the day after McDowell dropped some early shots.
Furyk was not playing beautifully but was still making sure to score, but it all fell apart for him on the back nine as wild tee shots saw him drop shots at both 13 and 16. He still had a chance to tie at the last, but pulled his approach into the bunker to effectively seal his fate.
McDowell, on the other hand, dropped four shots on the front nine but dragged himself back into contention with back-to-back birdies at 11 and 12. Another vital birdie at the 17th kept his hopes alive, before he set up the do-or-die opportunity at the 72nd hole.
His decisive putt had the pace but never quite the line, sliding two inches to the left to hand victory to Simpson - who initially needed his wife to tell him he had triumphed.
Elsewhere, Lee Westwood started the day just three shots off the lead but saw his hopes of victory die at the fifth in unlikely circumstances.
Westwood's drive at the par-four hit a tree and stayed there - in similar circumstances to Lee Janzen at the same hole 14 years ago. On that occasion Janzen's ball fell back to earth after five minutes and the American went on to win, but Westwood was not so fortunate - as his ball stayed lodged in the canopy as he went on to record a double-bogey.
Forced to press on the back nine as a result, the Englishman dropped three further shots that nullified the effect of a fine eagle - that was so nearly an albatross - at the 17th, as he finished five-over for the tournament.
Prior to Westwood's finish, first round leader Michael Thompson had set the early clubhouse target, getting safely into the scorer's tent at two-over after a masterful final round of 67.
After four birdies and just a solitary bogey for the American he looked firmly in contention to at least be part of a Monday play-off, before Simpson edged him during the closing stages.
A number of players finished three-over for the tournament, including fellow Louisiana State University graduates David Toms and John Peterson. Another to finish three-over was Padraig Harrington, as the Irishman fought his way into contention before a bogey at the last forced him to settle for a closing round of 68.
The mistake came as the three-time major champion attempted to engineer a birdie but he had one moment to celebrate during the final round - a slam-dunk chip-in at the 13th that really gave him the chance to contend over the closing stages.
Jason Dufner was a another to end the tournament at three-over, making it three majors in a row in which he has had a major impact on the leaderboard over the weekend.
Ernie Els missed his chance to claim a third US Open crown, finishing four-over after two late mistakes when the pressure was on. A majestic eagle at the par-four seventh (after a drive to seven feet) looked like giving the South African the platform to go on and contend but a horrible mistake at the par-five 16th - short-siding himself with his pitch shot, and then seeing his putt up the slope roll back to his feet - crushed his hopes of a memorable win.
Els' compatriot Retief Goosen finished with Westwood at five-over, as did Casey Wittenberg, John Senden and Kevin Chappell.
Further down the field, Tiger Woods had a horror start to thank as he finished seven-over for the tournament after a final round 73. The final score was impressive considering the 14-time major champion was six-over after six holes on Sunday, but nevertheless saw him finish just outside the top 20 having shared the lead after 36 holes.
Indeed, Woods ended up tied with low amateur Jordan Spieth, who was safely in the clubhouse after a final round of 70 to pip 17-year-old Beau Hossler, who struggled manfully all day but succumbed to a final round of 76 - thanks in part to a double-bogey at the 18th - that left him nine-over for the tournament.
That was nevertheless better than Phil Mickelson, however, who completed his tournament at 16-over. Only six of the 72 players who played all four rounds ended up worse off than the left-hander.