OAKMONT, Pa. -- You don't win the U.S. Open if you aren't playing your best golf.
Indeed, Dustin Johnson was on top of his game entering the 116th U.S. Open at historic Oakmont Country Club, collecting six top-five finishes over his last nine events.
On Sunday, he converted that consistent play into the biggest victory of his life.
"I felt like I've been playing well all year, just hadn't quite got it done," Johnson said after winning his first major, shooting a 1-under 69 in Sunday's final round at the Open to finish with a three-shot lead over Shane Lowry, Jim Furyk and Scott Piercy at 4-under 276 on Father's Day.
"So this was definitely a good time to get it done. But I had a lot of confidence in my game coming into this week."
Johnson's win didn't come without controversy.
He ran into trouble on the 5th green, when his ball moved before a par putt after he placed his club behind the ball and then removed it.
A course marshal ruled he didn't ground his club, and he was not assessed a one-stroke penalty.
However, a United States Golf Association official notified Johnson on the 12th tee that they would be reviewing the situation after the round.
Upon review, the USGA assessed the penalty -- but it became irrelevant as the world's sixth-ranked golfer kept his composure to earn his 10th PGA Tour victory in 193 events.
"I felt like I wasn't going to be penalized, so I just went about my business," Johnson said. "Just focused on the drive on 12 and from there on out, that we'd deal with when we got done."
Johnson nailed that drive 365 yards.
The 31-year-old American had finished second twice in previous majors, including his heartbreaking three-putt collapse on the 18th green in last year's U.S. Open at Chambers Bay in University Place, Wash.
He also placed second at the 2011 Open Championship in Sandwich, Kent, England.
Johnson has at least one win on tour in nine consecutive seasons.
Lowry, who held a four-shot lead through 54 holes, couldn't maintain his advantage, stumbling through a seven-bogey 76 in the closing round with just one birdie.
The 29-year-old Irishman finished in a tie for second at 1-under (279) with Jim Furyk (66) and Scott Piercy (69), after missing a birdie putt on No. 18.
"Bitterly disappointed," Lowry said. "It's not easy to get yourself in a position I got myself in today. It was there for the taking and I didn't take it."
The 46-year-old Furyk, a native of West Chester, Pa., had five birdies before a bogey on No. 18, but was given a rousing hometown send off as he walked off the course.
"I had a ton of support this week from my birthplace" Furyk said. "I heard Lancaster, where I grew up. I heard Manheim Township where I went to high school. I heard all kinds of stuff from western PA."
"I heard every little town and borough through here. ... I had a lot of places claiming me. It was a lot of fun."
Andrew Landry fell off the top of the leaderboard entirely after his 66 was the lowest opening-round score ever in a U.S. Open at Oakmont gave him an 18-hole lead.
The 28-year-old from Austin, Texas, registered a 78 Sunday to finish tied for 15th at 285.
Jordan Spieth came up short in his quest to become the first back-to-back U.S. Open winner since Curtis Strange in 1988-89.
The world's second-ranked player shot a final-round 75, missing four putts -- all within five feet -- at No. 6 to card a triple-bogey.
"I was just trying to do a little too much," said Spieth, who finished tied for 37th at 9-over (289). "Instead of just firing a straight ball at the hole, trying to bleed some big cutter in, and I just double crossed it.
"From there, the pin is actually located on a pretty tough little spot, where it -- you know, if you hit your first putt too hard, then you're left with a little bit of trouble."
Spieth won last year's U.S. Open by one stroke after Johnson's historic collapse.
Day rose into a tie for fourth late Sunday, but ended his round at even par after consecutive bogeys on Nos. 17 and 18.
Fourth-ranked Bubba Watson closed with a 75 to wrap up the tournament tied for 51st at 12-over (292).
Brooks Koepka (68) flirted with Johnny Miller's course record 63, reaching 6-under after an eagle, six birdies -- including four in a row -- and a par on Nos. 4-11.
Koepka fell off the mark with five bogeys on his final six holes, ending up tied for 13th at 284.
"I was hoping for something even lower," Koepka said of Miller's 63 in the 1973 U.S. Open. "I was hoping for 60, 61. I thought that was pretty obtainable."
Masters winner Danny Willet of England had a miserable start with double-bogeys on Nos. 3 and 5, but birdied Nos. 6 and 7 before a bogey on No. 9.
Willet had three birdies opposite a bogey on the back nine, shooting a 71 to finish tied for 37th. In frustration, he smashed his putter in half -- the same one won with in Augusta, Ga.
"Yeah, unfortunately, it's now in two pieces," Willett said. "We'll have to get it refurbed, and then I won't be using it again."
Cabrera won at Oakmont in 2007 while Kaymer claimed victory at Pinehurst No. 2 in 2014.
NOTES: Rory McIlroy and Jordan Spieth, among others, spoke out on Twitter after Dustin Johnson's penalty at No. 5. "This is ridiculous. No penalty whatsoever for DJ. Let the guy play without this crap in his head. Amateur hour from USGA," McIlroy wrote. Spieth added: "Lemme get this straight. DJ doesn't address it. It's ruled that he didn't cause it to move. Now you tell him he may have? Now? This a joke?" ... Angel Cabrera's son, Angel Cabrera Jr., was his caddie on Father's Day. The Argentine's U.S. Open win at Oakmont was nine years ago Monday. ... Top-ranked amateur Jon Rahm's 7-over 287 was the best score among amateurs. "It's a special moment being where I am and being this course and today the last day of my amateur career," the Spaniard said after Sunday's 70. Rahm turns pro at next weekend's Quicken Loans National in Bethesda, Md. ... Tiger Woods, whose foundation hosts the Quicken Loans National, will attend the tournament, but won't play. Woods (back) hasn't played since last August. "I am making progress, but I'm not yet ready for tournament competition," he wrote on his website.