Koepka's wrist injury kept him on the sidelines for four months, a hugely frustrating time spent with his left arm in an elbow-length cast and watching lots of television. Koepka, now owner of four worldwide victories and No. 9 in the world, was then greeted by his girlfriend, Jena Sims, and other family and friends before making his triumph official in the scoring area.
Masters champion Patrick Reed, who briefly shared the lead with five birdies through seven holes, stumbled on the back and had to settle for a 68 to finish fourth.
Phil Mickelson, who finished Saturday with an 81 after letting frustration get the best of him when he hit a moving ball with his putter on the 13th green to earn a 2-shot penalty and a sextuple-bogey 10 on the hole, turned it around with a 69 to finish 16-over 296 in his 27th US Open. ". All the way around, I always felt like I could get myself back in it".
Aaron Baddeley was the best-placed Australian in 25th place after a closing 69 that included four birdies.
"Overall though I'm very happy".
Brooks Koepka waits to hit on the 12th hole during the first round of the Travelers Championship at TPC River Highlands on June 21, 2018 in Cromwell, Connecticut. Tony Finau and Daniel Berger played in the final group but Berger was never in the hunt from early in the day, and Finau came up just short, messing up the 18th hole with a drive into the fescue.
The Englishman almost got it: A birdie putt from 8 feet on No. 18 broke right and skidded past the hole.
Tommy Fleetwood is in the clubhouse with a 7-under 63, tying the record for the lowest round at a U.S. Open. Johnny Miller famously posted that score 45 years ago at Oakmont (Pa.) Country Club to complete a six-stroke rally for the title.
Fleetwood, whose fourth place behind Koepka at Erin Hills past year had been his best major finish to date, said: "I never thought I was out of it, I just needed a good start". Four under through seven and it was game on.
Koepka pulled a pitching wedge to the left, down the slope and into thick grass. Koepka was 6 over par, with just three birdies.
The biggest might have been his bogey on the nasty little par-3 11th.
But he was one of the first to congratulate Koepka before interviewing him for the TV viewers, telling him "hell of a job".
Koepka moved to a career-best No. 4 in the world ranking. Koepka's experiences stood him in good stead last week on a links-style course. "It's at my house, just chillin'", Koepka said. "I enjoy being pushed to the limit. Unfortunately (I) missed it, but it gets the rhythm, you feel good and it kind of leads to the rest of the round".
Golf analysts and competitors criticized the playing conditions in this year's tournament, and even the USGA apologized for some of the course conditions in the third round.
Even after the USGA Chief Executive Mike Davis came on the air late in the afternoon to admit the association made a few mistakes and allowed good shots to be penalized, it isn't clear that they really know where the line between hard and unfair really lies.