Kims four-round total of 266 smashed the previous tournament record by seven. Kelly Robbins and Val Skinner each posted 273s in 1996.
Webb carded a seven-under 64, and was followed in third place by two-time former champion Juli Inkster. Inkster, who was the second-round leader, shot a three-under 68 and came in at 16-under-par 268.
Hee-Won Han, who won last weeks Safeway Classic, managed a six-under 65 on Sunday and took fourth place at 14-under-par 270.
While Kim held off two Hall of Famers en route to her first victory, the story of Sundays final round might have been a 35-year-old journeywoman who has never won on tour.
Anna Acker-Macosko collected 11 birdies and no bogeys for an 11-under-par 60, matching the second lowest number in LPGA Tour history. Meg Mallon posted the same score in the second round of last years Welchs/Frys Championship and Jung Yeon Lee had a 60 in the opening round of the same tournament this year.
Annika Sorenstam owns the only 59 in tour history. She shot that in the second round of the 2001 Standard Register PING.
Acker-Macosko birdied her first two holes, then tallied three birdies in her final four holes on the front nine for a 31. She birdied her first two on the back side, then four more in a row from the 13th to get to 11-under par for the round.
At the 17th, Acker-Macosko left her 25-foot birdie putt short. She had a 30- foot putt at the last to become the second player in LPGA Tour history shoot the magical 59, but the putt was too far right and instead she tapped in for a par and 60.
It was a straight putt and I was reading it to break, said Acker-Macosko, referring to her missed putt at the 18th. Its probably the closest Ill ever come to tying one of Annikas records.
Acker-Macosko tied for fifth place with Jeong Jang (62) at 13-under-par 271.
Inkster held the lead throughout most of the round and the margin was three after the 11th. Kim had three birdies and one bogey at that point, but was poised to make her charge.
Kim birdied the 12th and 14th holes to get within one of Inksters lead. When Inkster bogeyed the 14th, that dropped her into a three-way tie for the lead with Kim and Webb.
Kim and Webb both birdied the 15th hole to share a one-shot lead with Inkster in the group behind. Inkster parred the hole to fall one off, but Kim took a two-shot lead with a birdie at No. 17.
Kim had a one-shot lead on 18 and missed her birdie putt left. Webb had close to nine feet to tie Kim, but missed the putt, giving Kim her first win after several close brushes with the winners circle.
She has posted four top-15s in her last four starts and took second to Cristie Kerr at the State Farm Classic. Kim missed a short putt on the final hole in that event to lose by one.
Mi Hyun Kim (66), Michelle Estill (68) and Katherine Hull (68) tied for seventh at minus-12.
Liselotte Neumann (66) and Donna Andrews (68) shared 10th at 11-under-par 273.