ERIN, Wis. -- As Brooks Koepka made the walk up the 18th fairway to a standing ovation early Sunday evening, he was aware that his first major championship was well within his grasp.
The 27-year-old American didn't realize, however, just how close he was to making history.
Koepka strung together three consecutive late birdies and shot a 5-under-par 67 in the final round of the U.S. Open at Erin Hills.
Koepka entered Sunday in a three-way tie and a shot behind 54-hole leader Brian Harman. He used the pivotal stretch to pull away and finish the championships at 16-under 272.
His finish equaled the scoring record for score in relation to par that Rory McIlroy established in 2011 at Congressional Country Club.
"That's awesome," Koepka said. "I think it's really cool. It hasn't sunk in, obviously, and (it) probably won't for a few days."
Koepka was four strokes better than Harman, who shot even par on Sunday, and Hideki Matsuyama of Japan, who shot 6 under Sunday to finish the championships at 12 under along with Harman.
Tommy Fleetwood of England finished fourth at 277.
After hitting a short par putt on 18, Koepka -- playing a group ahead of Harman -- pumped his fist twice in celebration.
Koepka moved to 14-under with a birdie at the par-5 14th hole. After his second shot found the bunker, Koepka made an impressive shot to set up a short birdie putt to provide him with a two-stroke lead.
He followed with birdies at 15 and 16 to suddenly widen his gap to four shots and close in on the Open championship.
Koepka carried a one-stroke lead into the back nine after a birdie at No. 8, but quickly fell back into a tie with Harman. Koepka bogeyed the par-4 10th hole, marking the first time he registered a bogey on the back nine during the tournament.
Like Koepka, Harman hadn't bogeyed a hole on the back nine until Sunday.
Tied with Koepka at 13 under, Harman missed his par putt at the par-4 12th to fall a shot off the lead. Harman bogeyed his second straight hole at 13 to fall two shots behind Koepka.
Harman finished with a bogey on 18.
"I was pretty content making pars on the front nine because I knew the kind of day it was," Harman said. "But you've got to tip your cap to him. He went and won the golf tournament on the back nine. I've done it before, but he did it today.
"I had an opportunity today and didn't get it done. At the same time, I don't feel as if I lost the golf tournament. I just think Brooks went out and won the tournament."
After his birdie at 14, Koepka wasn't aware of Harman's bogey back at 13.
Nonetheless, the birdie that started the string of three straight did wonders for Koepka's confidence. But a par at 13, Koepka admitted afterward, meant even more.
"That was kind of the changing point of the round for me," he said.
As Koepka picked up momentum, Harman began to lose steam. And once Koepka made his third straight birdie at 16, Harman knew his championship chase was over.
"After that, it was kind of lights out," Harman said.
Justin Thomas, who shot a 9-under 63 on Saturday -- a record in relation to par -- to reach Sunday's final pairing while in a second-place tie with Koepka and Fleetwood, struggled in the final round with a 3-over 75 and tied for ninth at 280.
Like Harman, Thomas couldn't match Koepka's final-round mastery, which came on Father's Day. It was an accomplishment that wasn't lost on golf's newest major champion, even if his father and other family members weren't in attendance at Erin Hills on Sunday and missed one of Koepka's appearances at a major for the first time.
"That's probably one of the coolest things I've ever experienced and to do it on Father's Day, it's pretty neat," Koepka said. "I didn't exactly get my dad a card, so this works."
NOTES: Scottie Scheffler, who plays collegiately for the University of Texas, was the top amateur finisher at 287 for the tournament with a Sunday round of 73. Scheffler finished ahead of Texas A&M's Cameron Champ, who entered Sunday's final round with a two-shot lead over Scheffler, shot a 4-over 76 to finish at 288. ... The 54-hole leader, Brian Harman, entered Sunday's final round attempting to become the first left-handed player to win the U.S. Open. Only four left-handers -- Bubba Watson, Phil Mickelson, Mike Weir and Bob Charles -- have won major championships. ... Jordan Spieth, who shot his lowest round (69) of the championships on the tournament's windiest day, said he wouldn't mind seeing the event return to Erin Hills. "I think it's an awesome golf course. I think that's been the consensus from everyone," Spieth said Sunday. "There are so many (courses) to choose from, (but) I'm sure at some point, it will come back here."