Japan's Akie Iwai fired six birdies in a six-under par 66 to win the Portland Classic by four strokes and join twin sister Chisato as a first-time LPGA winner in their rookie season on the US tour.
Iwai started the day at Edgewater Country Club with a two-stroke lead and never faltered to finish with a 24-under par total of 264.
Chisato Iwai was among the golfers trying to apply pressure, charging up the leaderboard with an eight-under par 64, but it was American Gurleen Kaur who finished second after an impressive, bogey-free seven-under par 65 for 268.
Former US collegiate standout Kaur, opened with three straight birdies and had four more coming in for her career-best LPGA round.
Akie Iwai became the 10th first-time LPGA winner this season and the fifth Japanese player to triumph.
She said she'd felt pressure to join the flood of Japanese winners, but even more she was inspired by her sister's triumph at the Riviera Maya Open in Mexico in May.
"(She) really inspired me," said world number 29 Iwai, who was runner-up this year at Thailand and the LA Championship. "That's why I did my best this year."
Iwai got off to a steady start, with back-to-back birdies at the fifth and sixth and two more at 11 and 14.
She got up and down for par from off the green at 16, then capped her day with another birdie brace, curling in a testing birdie putt at 17 before draining an 18-footer at 18.
"Today I was able to conquer myself," she said.
Her sister, who had been watching the final holes nervously, was the first to rush the green and start the champagne-spray celebrations.
"Just watching, so nervous," Chisato said as Iwai was coming down the final stretch. "I'm cheering for her."
But first she had been chasing, and hard.
Chisato started the day seven adrift but after an early bogey exploded with eagles at the fifth and seventh – with a birdie at the sixth sandwiched between.
She strung together four straight birdies from the ninth through the 12th and rebounded from a bogey at 15 with one last birdie at 17.
She finished tied for third on 19-under 269 with Sweden's Linn Grant, who rolled in the seventh birdie of her five-under 67 at 18.
Australia's Grace Kim, who captured her first major title at the Evian Championship last month, started the day two shots off the lead and carded a two-under 70 that left her in sole possession of fifth place on 270.