"I didn't expect to be sitting here at the start of the day," Webb said. "Even, actually, when I finished the day, I didn't expect to be sitting here. So I feel a little bit lucky, I guess, to be sitting here. But it doesn't make it feel any less special."
She took the lead with a course-record 9-under 63, then waited 90 minutes to see if anyone could catch her. No one did.
"I thought best-case scenario I was in a playoff," Webb said.
Webb is close friends with founding player Louise Suggs and has a deep appreciation for the 13 women who started the LPGA Tour in 1950.
"It's a very special event," Webb said.
For the second time in the event, Webb overcame a six-stroke deficit in the final round. In 2011 in the inaugural tournament, she finished with a 66 for a one-stroke victory.
"I just love the feeling of this event," Webb said.
Webb donated $50,000 of her $225,000 check, giving $25,000 each to LPGA-USGA Girls Golf and "The Founders" documentary movie. She did an interview for the film this week and learned that only about 10 percent of the necessary money had been raised to complete the project.
"I was just standing on the 18th green when Mike (Whan, LPGA Tour commissioner) was introducing me, and it just came to me that, 'You know, I would love to be a part of that movie being produced.'"
Webb talked Friday night with the 90-year-old Suggs, a fixture at the tournament the last three years but unable to make it this year.
"She told me that I had to go out and shoot 64 yesterday, which I let her down and I didn't do that," Webb said. "So, I made it up to her today."
She certainly did.
Webb had 10 birdies and a bogey, playing the back nine in 6-under 30. She birdied five of the last six holes, making a birdie with a 20-footer on the par-4 18th to finish at 19-under 269.
"I definitely putted probably the best I have all week," Webb said. "Worked on a few things last night and really got the ball rolling on the back nine."
Webb also rallied to win the Women's Australian Open last month and has 41 LPGA Tour victories to match founding player Babe Zaharias for 10th place.
Ko, the third-round leader, parred the final three holes to finish a stroke back along with 2013 winner Stacy Lewis, Azahara Munoz, Amy Yang and Mirim Lee.
The 16-year-old Ko shot 70. She had a three-stroke lead after birdieing Nos. 2-5, slipped back with bogeys on Nos. 6, 9 and 11 and pulled within one with a birdie on the par-5 15th.
"I tried to get myself together," Ko said. "I made some bogeys at the wrong time, which wasn't ideal, but I tried my best until the last."
Munoz and Yang, playing together in the third-to-last group, missed long birdie putts on 18 and each shot 67. Lee shot 69 in the next group, also missing a long birdie try.
That left Ko and her 25-foot try on the last was just short and right.
"I played really well overall, so I'm just going to take the positive out of it," Ko said.
Lewis birdied the final two holes for a 66.
"It was just really nice to hit the shots and make the putts at the end," Lewis said. "Seeing putts go in always helps going into the next couple of weeks."
DIVOTS: Korda, playing with Ko in the last group, had a quadruple-bogey 8 on the par-4 seventh after hitting her approach into the desert, then played the final 11 holes in 5 under to tie for seventh at 17 under. The Bahamas winner shot 70. ... Hee-Won Han also matched the course record with a 63 to tie for 15th at 14 under. Playing in the ninth group of the day, she holed a sand wedge for eagle on No. 7. Ai Miyazato set the course record last year and Cristie Kerr matched it Saturday. Kerr finished with a 67 to tie for 10th at 16 under. ... Top-ranked Inbee Park closed with a 67 to tie for 10th.