Lewis stated at the start of the week that she would donate her entire prize money from the tournament to the relief fund for victims of the devastating floods in Houston, where her husband Gerrod Chadwell is women's golf coach at the University of Houston.
"I have been hitting solid and [gave] myself a lot of really good chances for birdie".
Hurricane Harvey has killed around 50 people and unleashed massive flooding that damaged up to 50,000 homes in Houston.
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However, Lahiru Thirimanne (67) and Angelo Mathews (55) upped the ante and shared a 122 runs stand between them. Only Indian superstar Sachin Tendulkar is above the pair on the all-time list of ODI hundreds with 49.
Lewis, who has 11 career LPGA victories, has six top-10 finishes this season. A trio of golfers are just two shots back heading into the weekend including Jodi Ewart Shadoff, Ai Miyazato - who is playing in her final LPGA Tour event on U.S. soil prior to retiring, and Moriya Jutanugarn. "It was a really tough shot and to see it go in just made me really happy and it changed my day. Everybody talks about it", she said.
Lewis grew up in The Woodlands, outside Houston, and lives nearby with Chadwell, so it was especially hard for her to be away from home when the hurricane hit with calamitous impact.
"You know, when I said that I had the goal of winning the tournament-you got to get a lot of things right, to go your way", Lewis said standing off the 18th green.
Lewis took a three-shot lead into Sunday and then held off a strong final-round charge by In Gee Chun.
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A Soyuz capsule carrying her and two other International Space Station crew members safely landed on time in Kazakhstan. Altogether, Whitson has spent 665 days off the planet, more than any other American - also more than any other woman.
Indeed, it was her second-lowest single round score of the year (she shot a 63 at the Pure Silk Bahamas LPGA Classic in January, the first event of the year). So was her parents' home, but she said the stories coming out of Houston moved her. Chun missed a short birdie putt at the par-4 14th, and pulled to within a stroke with a 45-foot birdie at the par-3 16th.
It was her first victory since 2014 and couldn't have come at a better time for Houston.
Chun's flawless 66 was plenty enough to earn her outright second place, with Brittany Altomare (69) a distant third on 14 under along with Moriya Jutanugarn, who began the final round as Lewis' closest challenger but stumbled to a disappointing 72.
Lewis, 32, has endured some frustration trying to collect her 12th LPGA title.
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One expert said the size of Sunday's detonation meant it was possible it could be a hydrogen bomb test. South Korea's Yonhap News agency says a magnitude 5.6 quake has occurred in North Korea.