NORTH PLAINS, Ore. (AP) -- Hilary Lunke walked off the course as the new U.S. Women's Open champion, smiling until she saw her father. Then, she burst into joyful tears.

With a sure putt that stymied her opponents in Monday's three-way playoff round, Lunke became the first qualifier to win the most prestigious trophy in women's golf.

And she sealed her fate with a clutch 15-foot birdie putt on the 18th hole.

''She's just got a tremendous amount of guts,'' said Lunke's father, Bill Homeyer.

After watching Angela Stanford make a 20-footer on the final hole for a share of the lead, Lunke completed a dramatic week at Pumpkin Ridge with a putt that broke sharply to the left and dropped into the cup.

Stanford and Kelly Robbins watched in awe. Lunke thrust her arms in the air and hugged her husband Tylar, her caddie.

The couple, married in August, just bought a home last week in Austin, Texas. Part of her $560,000 paycheck for the victory will go to the house.

''I guess we're going to have to call our mortgage broker and change our plans a little bit,'' she said.

Lunke finished with a 1-under 70, a stroke up on Stanford. In 22 events on the LPGA Tour, she never finished better than 15th.

Lunke became the first player since Annika Sorenstam in 1995 to earn her first LPGA victory at the U.S. Women's Open. And at 24, Lunke became the youngest American to win a major championship in 16 years.

''She was into her game and she knew what she needed to do,'' said Robbins, who finished two strokes back with a 73. ''And she did what we all hope to do, pull it off when we need to.''

Lunke had a chance to win outright Sunday, but her 12-foot birdie putt on the final hole came up short.

Not this time.

Lunke took only 23 putts in the 18-hole playoff, and the final one was her best stroke of the day.

''I can barely even remember hitting the putt,'' she said. ''I was just trying to trust my stroke, trust the fact that I've holed putts like that.''

Stanford, who trailed by four shots with 10 holes to play, pulled off more magic by chipping in for birdie on the 14th hole to finally catch Lunke. Her only mistake on the back nine cost her the victory.

From the 17th fairway, Stanford pulled her approach into the bunker, blasted out to 10 feet and missed the par putt.

Her only hope was a birdie on the last hole, and that looked unlikely when her third shot out of deep rough came up just short of the green. But Stanford, coming off her first LPGA Tour victory last week, again rose to the occasion.

But afterward, in the back of her mind, she figured Lunke would still pull it off.

''I know what it feels like when you're putting that well, every time you get over a putt you think, 'I'm going to make this,''' Stanford said. ''I know she was standing over it thinking, 'I know I'm going to make this.'''

Lunke hit only eight greens, hardly the recipe required for the U.S. Women's Open. But whenever the pressure was at its peak, Lunke always answered with clutch putts. Her birdie on the 18th was the ninth putt she made from 5 feet or longer.

Robbins, a major champion with nine LPGA victories, had experience and momentum on her side after closing with a 69 on Sunday. She recovered from a bad start to get within one shot, only to see her hopes end with a double bogey on the 13th hole.

Lunke looked as if she might remove all the drama from the first three-way playoff at the U.S. Women's Open since 1987. Despite relatively easy pin placements, all three women struggled at the start, only Lunke thrived.

Her short game was brilliant, especially the flat stick.

Lunke didn't hit a green in regulation until No. 6, where a 20-foot birdie putt moved her to 2 under and gave her a four-stroke lead.

Robbins and Stanford didn't let it get worse.

Robbins was wild off the tee and started with three bogeys on the first four holes, getting back into the mix with three birdies, including a 4-footer on No. 10 that brought her within one shot.

It looked like Robbins might leave the 10th green in a tie, but Lunke saved par from the bunker with an 8-foot putt.

Stanford, shaky off the tee and with her putter, fell to 3 over when she missed the green to the left on No. 8 from the fairway.

She didn't make another bogey until No. 17, which ultimately cost her a chance to win.