She finished at 18-under-par 195 after a final round of 66.
A week after coming runner-up at the Women's PGA Championship major, Park was consoled with her seventh LPGA Tour victory.
She was not thrilled with her front nine on Sunday -- two birdies and a bogey -- but four birdies on the inward half sealed the deal.
"My round today didn't go as well as I thought it would," she said. "I knew that it was important to make a lot of birdies on the front nine.
"There were a lot of opportunities that I missed but I talked with my caddie, and we both said there's still a lot of hope left, and we waited."
The 25-year-old is the third double LPGA winner this season, joining compatriot Ko Jin-young and Canadian Brooke Henderson.
Park is projected to displace Ko atop the world rankings, according to the LPGA.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Greg Stutchbury)
