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 36 players did not finish because of fading light.
Koepka finished two behind clubhouse leader Russell Henley on two under while DeChambeau ended two over.
Rory McIlroy rushed to finish, jogging up the last before rolling in a birdie, to card a one-under 70 in California.
World number three Jon Rahm also completed his round just before darkness descended, parring the ninth to sign for a 69 and sit alongside Masters champion Hideki Matsuyama and Americans Xander Schauffele and Hayden Buckley.
America's Henley was joined on four under by Louis Oosthuizen but the South African must complete his opening round on Friday because the hooter sounded to signal the end of play while he was playing his 17th hole.
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.
Play is scheduled to resume at 06:50 local time (14:50 BST), although more morning fog is forecast on the Pacific coast.