Brooks Koepka fired a final-round 67 Sunday at Erin Hills to win the U.S. Open and wrap up his first major championship. 

Koepka, 27, matched Rory McIlroy's record for the lowest winning score to par at a U.S. Open by finishing at 16-under.

Tied for the lead with six holes to play, Koepka made an 8-foot par putt on the 13th hole. As Brian Harman began to fade, Koepka poured it on with birdies over the next three holes, lightly pumping his fist after each one.

His reaction was subdued, just like his close friend and last year's U.S. Open champion, Dustin Johnson.

It capped quite a journey for the 27-year-old Floridian.

Without a card on any tour when Koepka got out of Florida State, he filled his passport with stamps from the most unlikely outposts in golf while playing the minor leagues on the European Tour -- Kazakhstan and Kenya, Portugal and India and throughout Europe.

It was at the U.S. Open three years ago when Koepka tied for fourth that helped earn a PGA Tour card, and he powered his way from obscurity to his first Ryder Cup team last fall and now a major champion.

Harman's chances ended with two straight bogeys, and a bogey on the par-5 18th hole gave him a 72 and a tie for second at 12-under with Hideki Matsuyama of Japan, who closed with a 66. Matsuyama didn't need to stick around very long. Koepka simply couldn't miss.

Koepka also became the third American to win the U.S. Open after Dustin Johnson's victory at Oakmont last year and Jordan Spieth's win at Chambers Bay in 2015. The last time Americans won the U.S. Open in three straight years was 1998-2000 (Lee Janzen, Payne Stewart and Tiger Woods). 

The Associated Press contributed to this report.