Creamer, who will walk in her high school graduation on Thursday, became the second youngest winner on tour at 18 years, nine months and 17 days. Marlene Hagge won twice as an 18-year-old, and both times she was younger than Creamer was in her win Sunday.
Jeong Jang birdied 17 and 18 to close a round of 4-under 67. She ended at 5-under-par 279 alongside Gloria Park, the 2002 champion here.
Christina Kim had a chance to force a playoff at the par-5 closing hole, but she left her second shot in a greenside bunker. She was unable to hole her third shot for eagle and walked away with a par for a round of 73 to end at minus-4. Heather Bowie and Joo Mi Kim were one stroke further back at 3-under-par 281.
Creamer, who opened the round one stroke behind Christian Kim, struggled throughout her round with the damp conditions. She stumbled to a bogey on the second to fall out of the lead at minus-5.
The youngster bounced back with a birdie from 12 feet out on the fourth at Wykagyl Country Club to get back within one stroke of the lead.
She came right back with a birdie on five to get to 6 under and a share of the lead with Park. Creamer, as well as Park, bogeyed the seventh to stay tied for the lead.
Creamer faltered to another three-putt bogey on the ninth to drop back to minus-4, and a tie for the lead with Park, who bogeyed the eighth, and Siew-Ai Lim.
The leaders continued to struggle though. Lim fell off the pace with bogeys on 11 and 13 and a double bogey on 16. Creamer maintained a piece of the lead despite a bogey on the par-4 11th.
Creamer converted an excellent up-and-down par on the par-3 13th. That gave her the momentum she was looking for. The rookie grabbed the outright lead at minus-4 with a kick-in birdie on the 14th.
She made it two straight birdies as she chipped within inches of the cup at the par-5 15th. Jang, playing three groups ahead of Creamer, birdied the last to tie Creamer at 5 under as Creamer parred 16 and 17.
Creamer's second to the par-5 18th came up short in the left rough. She pitched to 17 feet and drained the birdie putt for the win.
'I was actually thinking more about the second putt if I missed it coming back, because I knew Gloria blew her putt about five feet past the hole,' Creamer said of her putt on 18. 'I thought, there's no way I'm going to do that, it's just going to get to the hole. And it barely fell in. I didn't think it was going in at first. I think it willed its way into the hole.'
Jang started the round at 1 under and slipped to even par with a bogey on the par-3 fourth. The Korean reeled off three birdies in a four-hole stretch from the eighth to move into contention.
The 24-year-old stumbled to a bogey on 13, but recovered with a birdie on the 15th. Jang birdied the last two holes to share second place.
Park got to 6 under with a birdie on No. 2. She slid all the way back to minus-3 after bogeys on seven, eight and 11. She got one stroke back with a birdie on 13.
After a bogey the 14th, Park birdied the 15th to get to minus-4. She birdied the 17th, but could only par the last to share second place.
'It was a really great week,' said Park. 'Today I think I played really good for the conditions, but I wasn't happy with the putts I missed on seven and 11, which were short ones. Other than that, everything was good.'
Mi Hyun Kim posted a 1-over 72 to end at 2-over-par 282. Tina Barrett, Soo-Yun Kang and Michele Redman shared eighth place as the last players in red figures at 1-under-par 283.