Little-known American Andrew Landry was leading the US Open by one shot from two-time Masters winner Bubba Watson when play was suspended for the day because of thunder storms at Oakmont Country Club. Only nine players had completed their opening rounds when play was suspended at 20:51 BST, when the world number 624 was on three under par after 17 holes.
England's Lee Westwood is one under par through 13 holes, while Rory McIlroy is three over par after 12. The Northern Irishman's rival and last year's US Open champion Jordan Spieth is one over after 11.
Westwood, 43, started on the 10th and holed a 124-yard wedge shot for an eagle on the par-four 15th. Later, however, he missed a three-foot birdie putt on the 17th, which meant he had completed nine holes in two under.
The Englishman dropped back to level par after bogeys on the first and second. But he birdied the par-five fourth before officials halted play during a rain-interrupted first day in Pittsburgh.
Meanwhile, Spieth - the current world number two - started his round on the 10th and had a birdie on the par-five 12th. However, the 22-year-old Texan lost a shot with a bogey on the 14th.
Elsewhere, American amateur Scottie Scheffler completed his first round by shooting a one-under-par 69, while Jason Day, six-time runner-up Phil Mickelson and England's Justin Rose have all yet to start their first rounds.