Park has set records throughout the event. She established a new 18-hole mark in the first round (62), set a new 36-hole mark of 129 and her three-round total of 200 snaps the previous record of 201, which was set by Cristie Kerr and Annika Sorenstam in 2002.
Speaking of Kerr and Sorenstam, they share second place at 13-under-par 203 after both posting rounds of 69 on Saturday. Lorena Ochoa carded a 71 and stands at 11-under-par 205, while defending champion Sophie Gustafson (70), Juli Inkster (69) and Catriona Matthew (72) are tied for fifth at minus-10.
Park stumbled out of the gates with a three-putt bogey at the par-5 third. She bounced back with a birdie from 12 feet out on the fifth at Bighorn Golf Club to get to minus-15.
The Korean was briefly joined there by Kerr, who birdied her first five holes. Kerr later fell off the pace with three bogeys over a six-hole stretch.
Park cruised around the turn with five straight pars. She made another 12-foot birdie putt at the 11th. At the next, Park pitched her third within one foot and kicked that in for birdie to get to 17-under and five strokes clear of the field.
Park again three-putted for bogey at the 14th. She came right back to sink a 10-foot putt for birdie at the next. However, at the last she lost her drive well right into the desert.
After a lengthy search, a fan found Park's ball under a bush. She took a penalty drop for an unplayable lie, then took a free drop because there was a scoreboard in her way. She eventually two-putted for bogey to see her lead drop to three.
'I'm not showing it, but I'm extremely frustrated, but I'm sure there are a lot of frustrated golfers out there today,' Park said. 'Nobody really went deep today and the conditions weren't any tougher than the first two days.'
Park, who owns five tour wins, led entering the final round in each of those five events. Earlier this year at the Wachovia LPGA Classic, she held the lead entering the final round, but Lorena Ochoa fired a final-round 65 to beat her. That was the lone time she lost when entering the final round with the lead.
'I need all the help I can get,' said Park of heading to the final round with the lead. 'I like to get all of the help I can get. Hopefully I will shoot the lowest number again and finished at the top, which will be great.'
Kerr got off to a flying start. She sank a 5-foot birdie try at one and then dropped in a 6-footer for birdie at two. Kerr got up-and-down for birdie at the third to move to minus-13.
The 27-year-old drained a 40-foot birdie putt at four and capped a run of five straight birdies by draining a 12-foot birdie try at five.
Kerr hit a poor pitch at nine and it led to her first bogey of the round that dropped her out of a share of the lead. She hit a poor tee shot at the par-3 13th and that led to a bogey.
Kerr left her first putt well short at the next and walked away with a three-putt bogey that dropped her to minus-12. She responded with a birdie at 15. Kerr was unable to save par from over the green at 17, but closed with a 12- foot birdie putt at the last to share second.
Sorenstam was steady to start her round as she picked up one birdie over the opening 11 holes. That birdie came at the fourth when she drained a 3-foot putt. The Swede birdied the par-5 12th for the third straight round to get to minus-12.
The women's world No. 1 drained a 7-foot birdie try at the 15th. Sorenstam slipped to a bogey at the 17th when she missed a short par putt. However, like Kerr her playing partner, Sorenstam birdied the last to end at 13 under par.
'I thought I actually played really good,' Sorenstam said. 'I had a lot of chances. I wish I would have made a few more, but that's okay.'
Jeong Jang and Women's British Open champion Karen Stupples share eighth place at 9-under-par 207. Karrie Webb is one stroke further back at minus-8.