Miriam Nagl carded a 72 to join Siew-Ai Lim, Hee-Won Han and Michele Redman at 3-under-par 139. Heather Bowie followed at 2-under-par 140.
Creamer started on the back nine at under cold and dreary conditions at Wykagyl Country Club and hit a 9-iron to 15 feet for a birdie at the par-4 12th. Creamer then landed her tee shot inside 3 feet for a birdie at the par-3 13th, but gave that shot back with a bogey at the 14th.
The 18-year-old countered with a birdie at the very next hole and ran home a 12-foot putt for another birdie at the par-3 16th. Creamer then chipped her third shot to 2 feet for a birdie at the par-5 18th to take the outright lead around the turn at 6 under.
Creamer parred her next three holes, but made a mess of the par-3 fourth. She missed the green and chipped her second shot over the putting surface. Creamer then three-putted for a double bogey to fall back to 4 under. Creamer recovered with a birdie at the ninth for her share of first.
'I'm hitting the ball well,' said Creamer. 'For me, I think the most important thing is to know how to win and how to compete under pressure.'
Christina Kim, who held the lead after round one, also started on the back nine and tallied a lone bogey at the 14th. She made a move on the front side with back-to-back birdies starting at the second, but she dropped those shots with a double bogey at the fourth.
The 21-year-old found trouble again with a bogey at the eighth, but rolled in an 18-foot birdie putt at the ninth for a round of 72.
Park picked up a birdie at the 11th, her second, but stumbled to a bogey at the 13th. She answered with two straight birdies from the 15th, but struggled again with a bogey at the par-4 17th after her second shot found a bunker.
She hit an 8-iron to 5 feet for a birdie at the par-3 second, but bogeyed the following hole. Park countered with a birdie at the fifth, but bogeyed the sixth. She dropped another shot at the eighth, but responded with a birdie at the ninth.
'I'm going to try to hit some more fairways tomorrow to see what I can do,' said Park, who managed a 70 on Friday.
Joo Mi Kim played the back side first and collected four birdies over her first nine holes. She continued her fine play with back-to-back birdies from the first. Kim bogeyed the fifth, but picked up a birdie at the eighth en route to a 65.
Mi Hyun Kim posted a 72 to finish alone in 10th place at 1-under-par 141. Tracy Hanson, Jeong Jang and Celeste Troche were next at even-par 142.
Defending champion Sherri Steinhauer shot a 72 to finish in a group at 4-over-par 146. The halfway cut fell at 7-over-par 149 with 76 players qualifying for the weekend.