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Park claimed her second major title when she beat compatriot Ryu So-yeon and Japan's Nasa Hataoka in the sudden-death playoff after the trio finished tied on 10 under after four rounds.
Australian Sarah Jane Smith made eagle on the par-5 7th hole but only managed two birdies to go with three bogeys for a round of 71 and a total of four under, and a tie for 11th place.
Her compatriot, world No.9 Minjee Lee carded a 70 to be one under and tied for 25th while Karrie Webb's Sunday score of 72 left her four over and tied for 47th.
After a brief rain delay, Park made a 10-foot birdie putt on the par-4 16th hole at Kemper Lakes to beat Ryu at the second extra hole.
Teen Hataoko, after shooting an eight-under 64 on Sunday, dropped out after the first play-off hole with a par on the par-4 18th.
Ryu made a 20-footer for birdie from the fringe, and Park followed from 10 feet.
Park closed with a three-under 69 on Sunday while overnight leader Ryu had a 73, blowing a two-shot lead at the 17th.
She hit her tee shot left in the water on the par-3 en route to a double bogey.
The 24-year-old Park won the 2017 US Women's Open.
Americans Angel Yin (71) and Jessica Korda (69), on seven under finished tied fourth.
England's Charley Hull was a shot behind after a final-round 67, sharing sixth place with Canada's Brooke Henderson, who began the day second but faded with a 74.
