Collin Morikawa put it all together on Sunday, winning a major in just his second appearance and becoming just the fourth player to win a PGA Championship before his 24th birthday.

The 23-year-old American fired a bogey-free 64 to emerge from a crowded leaderboard and win by two shots over Dustin Johnson and Paul Casey at TPC Harding Park.

"I'm on cloud nine right now," said Morikawa. "It's hard to think about what this championship means. Obviously it's a major, and this is what guys go for, especially at the end of the their career. And we're just starting."

He picked up his third win on the PGA Tour, giving him more victories than missed cuts since he turned pro just 14 months ago.

Morikawa wrote an epic conclusion to one of the strangest weeks in major championship golf history. The PGA was contested without fans and it marked the first time a major champion had been crowned in 13 months due to the COVID-19 pandemic.

"Without a crowd it plays very different," he said. "But whether crowds were here or not, I still had to get it done, so I'm really happy about what just happened."

Morikawa joins Rory McIlroy, Jack Nicklaus, and Tiger Woods as players who have won a PGA before their 24th birthday.

Morikawa won the Workday Charity Open in July and the Barracuda Championship last year. He lost in a playoff at the Charles Schwab Challenge in July. His only missed cut on the Tour came at the Travelers Championship in June.

"This is just a lot of confidence, a lot of momentum, and it just gives me a little taste of what's to come," he said.

American Collin Morikawa celebrates with the Wanamaker Trophy after the 2020 PGA Championship at TPC Harding Park in San Francisco
American Collin Morikawa celebrates with the Wanamaker Trophy after the 2020 PGA Championship at TPC Harding Park in San Francisco GETTY IMAGES NORTH AMERICA / TOM PENNINGTON

"I got a taste of this now. Obviously it was a very crowded leaderboard. At one point, if you looked at the leaderboard it was all at 10-under and it was a party pretty much. So yeah, this one is going to be very special."

Morikawa made a 54-foot chip for birdie on the par-4 14th and an eagle two holes later on another par-4 to distance himself from the pack.

His eagle was set up by a 293-yard tee shot to just seven feet.

"Yeah, 14 was huge. I'd been hitting really great iron shots into there starting from 12, 12 through 14, but the chip looked really good.

"My caddie J.J. told me, 'Let's chip it in,' and that was the momentum I needed.

"We got to 16. He asked me what I wanted to do. I'm sure it was a split between hitting iron and going for it. Why not hit a great driver?

"I hit a great -- I just needed that one bounce to go forward, and it did -- and those are shots that you've got to take opportunities, and that's what really separated me."

The Californian is more familiar with the TPC Harding Park than most after attending college at the nearby University of California-Berkeley.

"I haven't been back since I graduated last year," he said. "So it's a pretty special place. To close it out out here at a course that I played a dozen times throughout college, it's really special."