Park, plagued by back trouble all season, had a 66 for an 11-under 133 at Bighorn while overnight leader Annika Sorenstam of Sweden slipped back with a 71 to finish alongside Wie and her fellow American teenager Paula Creamer, who shot a 69.
In only her second round as a professional, 16-year-old Wie enjoyed a flawless seven birdie round in her best performance after 86 rounds on the LPGA Tour.
It was one stroke less than her 66 as a 13-year-old in the Kraft Nabisco Championship third round at nearby Mission Hills where she tied for ninth -- the first of four top 10s in majors.
Wie made all her birdies in the first 12 holes and the most surprising came at the long seventh where she had to take an unplayable lie and then chipped in from 25-yards for four.
She also got lucky at the 14th where she again found her ball nestling in a bush but asked rules official Jim Haley for a free drop because the area was swarming with bees.
Under rule 1.4/11, whichallows for dangerous situations, her plea was granted and Wie went on to save par.
"Therewere tons and tons of bees and I remember watching golf on TV once when someone got relief for fire ants, and so I asked. I could have maybe played it, but it wouldn't have been a smart move" she said.
"Thedifference today was that I wasn't so nervous. I was much more at ease and had a lot of fun. I was just trying to make birdie after birdie and get to the top of the leaderboard. I'm pretty close but there is still room for improvement."
Park had a three-shotlead entering the final stretch in the championship last year before slipping back to finish three shots behind Sorenstam.
"Itwas sour last year, but now I'm very happy with the position I'm in," said Park. "I've been struggling with injuries all year but now I'm feeling good."
Sorenstam was tied with Park with two holes to play but dropped a shot at the 16th and another at the 18thwhere she hit her tee shot behind the scoreboard and was unhappy with the ruling from official Robert Smith.
"Ididn't get the relief I wanted because I still thought the scoreboard was in my way," she said. "But he said I could hit a straight shot so I had to accept it."