At a star-studded "designated event" with a purse of US$20 million, Clark – the 80th-ranked golfer in the world – broke away from the field with Saturday's third round of 63.

He followed up with a three-under 68 in what proved little more than a walk in the park on Sunday.

With a 19-under at Quail Hollow, Clark finished four shots clear of Schauffele, the World No.5.

Clark had not won in his first 133 events on the PGA Tour, dating back to 2019.

"It's been a long five years to get to this point on Tour," Clark said after collecting the US$3.6 million (A$5.33 million) winner's cheque.

"I thought I would have had one earlier, but it was well worth the wait and I'm so, so grateful.”

"There's so much that goes into this. There's so many times that I wanted to cry and break clubs – and I did break the clubs sometimes – in this journey, and to get to this point is so sweet."

Clark dedicated the win to his mother, who died from breast cancer while he was attending college.

"My mum obviously is not here. I wish she was but I know she's watching," he said.

Schauffele's final-round 70 was enough to secure outright second at 15-under, three shots clear of fellow American Harris English (69) and Englishman Tyrrell Hatton (70).

Scott closed with an even-par 71 to be the leading Australian, taking a share of fifth with England's Tommy Fleetwood (70) at 11-under.

Despite falling short of a 15th PGA Tour title, it was still Scott's best result in the US since a pair of equal fifths at the FedEx St Jude Championship and BMW Championship events last August.

Cam Davis (72) and Harrison Endycott (75) finished in a tie for 59th at two-over.