McIlroy and Clark lead Fowler early in US Open final round
Clark who started the day tied with Fowler at 10-under, birdied the first hole to briefly gain the solo lead, but dropped a shot at the second.
McIlroy birdied the first - nearly holing a 32-foot eagle putt - to reach 10-under.
The top three contenders, with world number one Scottie Scheffler in pursuit, were chasing a Hollywood ending at Los Angeles Country Club.
For Fowler and McIlroy it could be a story of resurgence - Fowler seeking to claim a first major title that once seemed inevitable after a slump that saw him plummet from fourth in the world to as low as 185th.
Northern Ireland star McIlroy, meanwhile, is seeking a fifth major title, but his first since he won the Open Championship and PGA Championship in 2014.
Clark, whose gutsy birdie at 18 on Saturday helped him claim a share of the 54-hole lead alongside Fowler, is in new territory, acknowledging that he found it "a little surreal" to be gunning for a first major just a month after breaking through for his first US PGA Tour title at Quail Hollow.
LA Country Club's North Course is hosting the championship for the first time after members of the exclusive club nestled amid the mansions of Beverly Hills were at last persuaded to share it with the wider golf world.
Results and reviews through the first three rounds have been mixed.
Fowler torched the course with 10 birdies in an eight-under-par 62 on Thursday - both records for a US Open round.
Schauffele stunningly matched that score less than half an hour later, and Fowler would add eight more birdies on Friday on the way to the halfway lead.
The low scores seemed far from the rugged test of skill and stoicism long associated with the US Open, but when the Southern California sun finally broke through to dry and firm the course, the challenge was clear.
Nevertheless, Sunday's early starters showed again that there were birdies to be had.
England's Tommy Fleetwood was eight-under for his round after rolling in a 20-foot eagle putt at 14 - his second eagle of the day to go with four birdies.
But he bogeyed the 16th and signed for a seven-under 63 that gave him the clubhouse lead at five-under par 275.
Regardless of conditions, the course - which was a mystery to most of the field when they arrived this week - has divided opinion.
"I just think the golf course is interesting, to be polite," said defending US Open champion Matt Fitzpatrick, who won at Brookline last year.
"There's just too many holes for me where you've got blind tee shots and then you've got fairways that don't hold the ball. There's too much slope... not my cup of tea."
