Webb finished at 14-under-par 270 for a seven-shot win over Hee-Won Han and Lorena Ochoa, claiming her second title of the season after the Kraft Nabisco Championship and the 32nd victory of her career.
Han also shot a 70 in her final round for her best finish this season, while Ochoa reached 7-under-par 277 with a 1-over 72.
Ochoa, who won the Takefuji Classic and finished second in a playoff to Webb at the Kraft Nabisco Championship, now has five-runner up finishes this year and three at this event.
Reigning Rookie of the Year Paula Creamer, 2005 champion Cristie Kerr and Pat Hurst tied for fourth place at 6 under. Creamer fired a 69, while Kerr and Hurst both struggled to 73s.
The old tournament scoring record was 275, set by Grace Park in 2003 and matched by Se Ri Pak the next year. Webb collected 21 birdies with seven bogeys over her four rounds to break the mark, and in the process moved into 15th place alone on the LPGA's all-time wins list.
It was almost too easy, as Webb entered the final round with a five-shot lead.
Still, she wasn't comfortable until late in the day.
'It's just hard to play with that sort of a lead than a one-shot lead or one behind, because you're trying to keep yourself in the same game plan as you have had for the last three days,' Webb admitted. 'But at the same time, you don't want to make too many mistakes.'
Ochoa was one of three players who began five shots off the lead. She birdied the first hole to get within four strokes.
'Out of everybody that was chasing me, Lorena was probably the one that worried me the most,' Webb said. 'She went out and birdied the first hole, so I knew it was game on from there.'
Webb responded with a birdie at the par-5 third after knocking a pitching wedge within 15 feet, then rolled in a 15-footer at the par-3 fifth to reach 15 under.
A three-putt bogey at the sixth was followed by another bogey at the eighth, but Webb was at 14 under around the turn after sinking a 25-foot putt at the par-4 ninth.
Bad weather moved into the area, delaying the round 1 hour and 42 minutes until 2:30 p.m. local time.
After the break, Webb played the back nine at even-par. She found a bunker and dropped a stroke at No. 15 before recouping the loss with a birdie putt at the par-4 16th, where she knocked a 6-iron within 15 feet.
Webb finally relaxed after that.
'After the putt,' she declared.
Reilley Rankin and Mi Hyun Kim shot matching 69s and shared seventh place with Jeong Jang (72) at 4-under-par 280. Jee Young Lee (67), Shi Hyun Ahn (67) and Joo Mi Kim (72) were knotted one stroke further back in 10th