Park, a two-time medalist, beat Paula Creamer 3 and 2 in Friday's semifinals while Wuesthoff bested Mina Harigae 2-up in the other semifinal contest.
Park and Creamer exchanged birdies early on but the big moment in the match came at the 12th hole. Creamer incurred a penalty stroke when her ball moved after addressing it. Now her putt for par became bogey and suddenly Creamer found herself 2-down.
Park birdied the 13th to go 3-up then Creamer missed a six-footer for par at 14 to lose the hole and fall 4-down. Creamer won the 15th when Park failed to get up and down from a greenside bunker.
The final hole of the match came at 16. Both players found the fairway and Creamer knocked her second to 20 feet while Park had 12 feet for birdie. After Creamer missed her birdie try, Park two-putted for her par and a spot in the final match.
'I am very competitive. I love to win,' said Park, through her coach Charlie Yoo. 'Tiger Woods plays to win and I have the same kind of attitude. Every time I go out to play I want to win.'
Wuesthoff bogeyed one and three to fall 2-down in the early stage of the match.
'I was frustrated being down two,' said Wuesthoff. 'My putting wasn't working at first, but I had confidence in my iron shots.'
Wuesthoff hung tough and with a par at the 11th, took a 1-up lead. She went 2- up with a par at the 16th and closed the door on the match at 18 when she scrambled for par from the left trees to make her first final in this championship.
'I played with In-Bee before. She's a great player,' said Wuesthoff. 'She hits the ball straight every time and she has a great short game. Tomorrow I'm just going to play my game, not her.'
The U.S. Girls' Junior Championship is one of 13 championships conducted annually by the United States Golf Association, 10 of which are strictly for amateurs. The U.S. Girls' Junior is open to female amateur golfers who have not reached their 18th birthday prior to the end of the championship and have a USGA Handicap Index of 18.4 or better.
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