Erin - Brian Harman staked an early claim to become the seventh straight first time major winner by grabbing an early lead in a low-scoring start to the 117th US Open here Thursday.
The American world number 50 made the most of benign conditions at Erin Hills Golf Course to move to four under at the turn, one ahead of a group of three players which included compatriots Rickie Fowler and Charley Hoffman.
Harman, teeing off on the par-four 10th at the Wisconsin course, rattled off four birdies and five pars in his opening nine holes to get off to a flier.
Fowler, the 2014 runner-up, made three birdies to move to three under.
The 7,441-yard layout at Erin Hills is the longest major championship course in history.
But a week of rain which has softened greens and made the fairways more forgiving made for a low-scoring start to the second major of the season.
The past six majors dating back to the 2015 PGA Championship have been won by players who have never won a major before, with Sergio Garcia the most recent to break his duck with his triumph at the Masters.
Harman could become the seventh if he triumphs this week.
A slew of players were two shots back from the leading trio on two under, including South African veteran Ernie Els and England's Lee Westwood.
Westwood recovered from a double bogey on his third hole to drain three birdies.
World number one Dustin Johnson, the tournament favourite, made a steady start in a star-studded grouping with 2015 champion Jordan Spieth and 2014 winner Martin Kaymer of Germany.
Johnson, the defending champion, was even through four holes while Spieth was one under.
But despite the kind conditions, there was at least one early victim on Thursday.
Billy Horschel got off to a disastrous start with a quadruple bogey nine on the par-five first hole.
Masters winner Garcia and world number two Rory McIlroy had afternoon tee-times scheduled.
Meanwhile, six-time US Open runner-up Phil Mickelson confirmed his withdrawal from the tournament on Thursday as expected.
Mickelson had vowed to skip the tournament to attend his daughter's high school graduation ceremony but had been granted a tee-time on the off-chance any delay in play may allow him to travel across the country to make the first round.
His place in the field was taken by Mexico's Roberto Diaz.