Two-time winner Brooks Koepka shone as defending champion Bryson DeChambeau faltered in a US Open first round that was left uncompleted because of fog.
A 90-minute delay to the start of play at Torrey Pines meant the later starters were hampered by fading light.
While Koepka finished two off the lead on two under, DeChambeau closed with a birdie to end the day two over.
Rory McIlroy rushed to finish, jogging up the last before rolling in a birdie, to card a one-under 70 in California.
America’s Russell Henley is the clubhouse leader, with South Africa’s Louis Oosthuizen also on four under.
Oosthuizen was on the 17th when the hooter sounded to signal the end of play and will complete his round on Friday.
England’s Matt Fitzpatrick, Tyrrell Hatton and Richard Bland all finished their rounds on one under, while Lee Westwood and Scotland’s Robert MacIntyre are one back after carding 71s.
Phil Mickelson, 51, is chasing a career Grand Slam but his slow start saw him finish on four over.
The San Diego native became the oldest major winner when he won his second US PGA Championship in May and is once again seeking to add the US Open title to his collection, having finished as runner-up six times.
Italian Francesco Molinari and Spain’s Rafa Cabrera Bello lead European hopes on three under par.
As the skies cleared the conditions were favourable for early starters, but those who began later had stronger winds to contend with and 36 players will have to complete their first round before starting their second on Friday.
More to follow.