SOUTHAMPTON, N.Y. — In 2009, Inbee Park followed her first United States Women’s Open title with the worst season of her career. Overwhelmed by sponsorship opportunities and overnight celebrity at age 19, she struggled handling the pressure to perform. Her game went south.

She entered Japanese LPGA qualifying school and wound up playing on the Japanese tour, filling a year-round golfing schedule. She altered her swing mechanics and disappeared into relative obscurity, but, in time, she rediscovered her confidence.

And since late 2012, she has soared past her peers on tour in the United States, becoming the latest in a string of players to stand out above the rest.

With a 74, Park won her second U.S. Women’s Open by four strokes at eight under par Sunday at Sebonack Golf Club. She became the first female player to win the first three majors in a season since Babe Didrikson Zaharias in 1950.

Five years after winning her first Open, Park made brutal Sebonack appear pedestrian, as one of only three women below par for the tournament.

“I just tried to stay calm and I think I did,” Park said. “I’m just very glad I could put my name in history.”

In her past 24 events, Park has won eight times and finished second five times, broadening the gulf between herself and the others in the LPGA field. She has become the latest iteration of the tour’s line of recurring champions, from Annika Sorenstam to Karrie Webb to Lorena Ochoa to Yani Tseng, who together amassed 24 major titles between 1995 and 2011.

Sorenstam, watching all week as an analyst for the Golf Channel, noted imperturbable composure.

For four days, Park’s expression hardly changed.

“She can still improve in some areas,” Sorenstam said. “And that’s a scary thought.”

Nothing seems to faze Park anymore, said her caddie, Brad Beecher. On the course, he avoided mentioning the possibility of another major victory, even with a multiple-stroke lead, until Park finished her third shot on No. 18.

“I said, Enjoy this walk,” Beecher recalled. “You’re about to join history.”

Park smiled. “Funny enough,” she said to him. “I don’t feel that nervous.”

Park said experience, and weekly conversations with a mental coach, have helped her remain calm during rounds. Her unusual cross-hand putting style, which she has used since she was 10, worked magic on Sebonack’s greens, where she finished tied for second in putting average (28.50) per round.

“Her eye for it at the moment, her feel for it,” Beecher said, “it’s the best I’ve seen.”

Sebonack, in just its seventh year of existence and bookended by two of the most recognizable courses in the nation, Shinnecock Hills and the National Golf Links of America, proved to be a stern test for the rest of the tournament’s field.

Weather was a continual factor. After heat baked the course early in the week, the wind off Great Peconic Bay picked up over the weekend, fierce enough to blow Angela Stanford’s scorecard right out of Lizette Salas’ hands on the 18th.

A heavy fog rushed in Friday evening, suspending play for 41 golfers in the second round.

When the sun returned Saturday, the greens and the fairways hardened again, adding another hurdle for golfers to overcome.

The course design — a Jack Nicklaus and Tom Doak collaboration — offered a blend of Nicklaus’ bunkers and strategy with Doak’s contoured fairways and greens, along a mile of bay coastline, with sandy dunes and deep fescue. Few shots came from flat lies. Few putts did not require multiple deviations.

The course flustered the former teenage sensation Michelle Wie, who withdrew 17 holes into her second round, at 11 over, with the official cause given as illness. It caused a rift between Jessica Korda and her caddie, Jason Gilroyed, midway through the third round. Korda abruptly fired Gilroyed after the ninth hole and replaced him with her boyfriend, Johnny DelPrete, who carried her bag the remainder of the tournament, which she completed at 1 over and in a tie for seventh place.

“It’s a U.S. Open, it’s tough out there,” Korda said Saturday. “It just wasn’t working out.”

Park entered Saturday’s round with a 2-stroke lead over I.K. Kim, but after bogeying three consecutive holes on the back nine, her play looked shaky for the first time all week. She rescued her round — and perhaps her eventual victory — with a 34-foot downhill birdie putt on the 14th.

On Sunday, mist and fog early in the day made conditions tricky for everyone. Jodi Ewart Shadoff, who began the day seven strokes back in third place, bogeyed her first three holes, quickly falling out of contention.

With that, the tournament was whittled to two — Park and Kim, her playing partner and Korean compatriot, gunning for her first career LPGA major. It all but ensured that an Asian-born player would win a 10th consecutive women’s major.

Kim, another sharp putter, birdied the second hole to cut Park’s lead to three strokes. But a bogey on the fourth set her back again, and Park pushed her lead to five strokes with nine holes to play.

“I had a good opportunity,” Kim said. “It was just hard to make mistakes.”

After bogeys on 14 and 15, Park finished with pars on the final three holes, sticking her third shot within 10 feet on the 18th. She missed the birdie putt by fractions of an inch — a pedestrian conclusion to a stunning achievement.

“It’s something I’ve never dreamed of,” Park said. “All of a sudden I’m there.”

Also on Sunday:

Haas triumphs at Congressional: BETHESDA, Md. — Bill Haas won the AT&T National and joined some distinguished company. Haas pulled away from a crowd of contenders with three straight birdies, two key pars and one good hop out of the rough. It led to a 5-under 66 on a muggy day at Congressional and a three-shot win over Roberto Castro. As many as six players had a share of the lead at some point until Haas rolled in a 10-foot birdie putt on No. 8. Worried about a splotch of mud on his ball, he hit his approach to just inside 12 feet for birdie on the par-5 ninth, and then hit a 5-iron to 10 feet for another birdie on the 10th. Haas led by at least two shots the entire back nine and finished at 12-under 272. Haas has won at least one PGA Tour event in each of the past four years, joining Phil Mickelson, Dustin Johnson and Justin Rose. The 31-year-old won for the fifth time in his career, and this was the first one with Tiger Woods on the property — not to play, but to hand out the trophy. Woods sat out this week with an elbow injury and won’t play again until the British Open.

Perry gets major win: PITTSBURGH — Kenny Perry won the Senior Players Championship for his first major title, overtaking Fred Couples with a final round 6-under 64. Perry finished at 19-under 261 at Fox Chapel, two shots ahead of Couples and Duffy Waldorf. The 52-year-old Perry opened with a 71 and shot consecutive 63s in the next two rounds. Couples closed with a 68, and Waldorf shot 64.

Casey tops Irish Open: MAYNOOTH, Ireland — England’s Paul Casey made a 50-foot eagle putt on the 18th hole to win the Irish Open by three strokes for his 12th European Tour title. Casey closed with a 5-under 67 to finish at 14-under 274 at Carton House. England’s Robert Rock and Dutchman Joost Luiten tied for second. Rock shot 71, and Luiten had a 74.