Cristie KerrKerr, who also lifted the trophy in Virginia in 2005, fired a final-round one-under par 70 for a 16-under total of 268.
In-Kyung Kim closed with a 71 for 270, while South Korean Song-Hee Kim (71) and Australian Lindsey Wright (73) shared third on 271.
Kerr picked up her first stroke of the day with a seven-foot birdie at the fourth, but she gave it back at the par-three 13th where she hit her second shot into the left rough.
At 15 she hit a nine-iron to 45 feet en route to a tap-in birdie.
Kerr had trailed by one when she arrived at 15, but her birdie, coupled with a double bogey on 16 by Song-Hee Kim put her in the lead.
In-Kyung Kim and Wright also bogeyed 16, where Kerr drained a seven-footer for par, to give the American a two-shot lead with two to play.
"Well, it was pretty tight all the way through there, until the last couple holes," said Kerr, who claimed her 12th LPGA Tour victory.
"I just tried to play my own game, tried to be good mentally on every shot, and the momentum kind of swung in my favor when I birdied 15.
"And I don't know who doubled 16, but somebody doubled 16, and that gave me good momentum going into the last couple holes.
"And the par save on 16 to get a two-shot lead instead of one going into the last two holes was big."
Wright's bogey at the last allowed In-Kyung Kim to finish alone in second.
Kerr said the Kingsmill course played tougher on Sunday than it had all week, thanks largely to the pin positions.
"It played really different today," she said. "Even though we had rain last night, the course didn't seem incredibly wet ... and they tucked all the pins today, which is why you saw the scores what they were."
Kerr said one of her biggest challenges was staying patient in the absence of birdies.
"I just stuck it out, stuck it out," she said. "I hit a lot of good putts that were just a little too hard or a little too soft to be able to make more birdies...
"And you know, I made a big par putt at 16, which was probably one of the best putts, I made a lot of birdies, but it was one of the best putts I hit today."
In-Kyung Kim's round included three birdies and three bogeys. She, too, found the greens challenging.
"Actually, the greens were faster than I thought they would be," she said. "You can't get too aggressive."
