Rickie Fowler made light of the longest course in major championship history with a "stress-free" and record-equalling start to the 117th US Open.
Erin Hills had been set up to play to 7,845 yards in the first round, surpassing the record set at Chambers Bay in 2015 by 150 yards, but a combination of wide fairways and a course softened by previous thunderstorms helped Fowler card seven birdies in a flawless opening 65.
That equalled the lowest score in relation to par in the first round of a US Open, Jack Nicklaus and Tom Weiskopf having both shot 63 in the first round on the par-70 layout at Baltusrol in 1980.
"It's always cool to be part of some sort of history in golf, but I'd rather be remembered for something that's done on Sunday," said Fowler, who finished in the top five in all four majors in 2014 but has yet to win one of the game's biggest prizes.
"I didn't see seven under at the start of the week, but today is the best we are going to get. I just kept making putts when it mattered.
"It was nice. You don't get many rounds at the US Open that are stress-free. I knew I needed to drive it well and from there was just able to manage hitting and continuing to swing well and hitting good shots and rolling a couple in."
Fowler, 28, who was 25 over par for his previous four rounds in the US Open, ended the day a shot ahead of compatriot Xander Schauffele and England's Paul Casey, with Tommy Fleetwood, Brian Harman and Brooks Koepka a shot further back.
Lee Westwood, who is seeking his first major title at the 77th attempt, carded a 69 which was matched by compatriot Andrew Johnston, but defending champion and world number one Dustin Johnson struggled to a three-over-par 75.
And Rory McIlroy, who said players might as well "pack your bags and go home," if they could not hit the wide fairways, found just five of them and slumped to a 78, despite having eagled the second by driving the green on the 330-yard par four.
Casey has recorded three consecutive top-six finishes in the Masters, but has just one top-10 in the US Open in 13 attempts.
"I would have snapped your arm off for six under," said the 39-year-old, who chipped in for an eagle on the first and added six birdies and two bogeys.
"I watched Rickie this morning and was hoping and praying if I could get the same kind of conditions I would be half as good as Rickie Fowler, so to be right behind him I'm ecstatic.
"This was a fun low round. I don't know that I've ever played a US Open where I've had that much enjoyment."
Fleetwood has made the cut in just one of his seven major appearances to date, but the 26-year-old from Southport made an ideal start with a birdie on his opening hole and added four more in a brilliant putting display.
"The course was as receptive as it's going to be but I never really tried to make a birdie, they just seemed to happen along the way," said Fleetwood, who finished second behind Johnson in the WGC-Mexico Championship earlier this season and lost in a play-off in the Shenzhen International in April.
"But towards the end I holed some great putts for par. No matter how fast you start or how many birdies you make, the pars are the ones that keep you in it. You don't really think about shooting five under at the US Open. Seven under is ridiculous."
Westwood's 69 was just the third time the former world number one has broken 70 in the first round of the US Open, with his lowest score of 67 coming last year.
"I played great," said the 44-year-old, who shot 80 when playing with eventual winner Johnson in the final round at Oakmont. "I missed one fairway, one green and that was the double bogey (on the 12th).
"My short game was great at Wentworth (in the BMW PGA Championship) but my ball-striking is really coming back to its best now and if I keep going then there's no reason I can't be in contention on Sunday."
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