The New Zealand golfer Lydia Ko is five shots off the lead in the second major of the year, after weather forced the abandonment of the PGA Championship in Illinois late in the first round.
Ko shot a one-under par 70 to be tied for 23rd five shots behind South Koreans Amy Yang and Chella Choi.
Yang, twice a major runner-up at the U.S. Women's Open, bogeyed the 17th hole to fall back to five-under and surrender the sole lead moments before lightning prompted the late afternoon suspension.
She is among 30 players who will return early tomorrow to complete the round at Olympia Fields.
Newly-crowned women's world number one Ryu So-yeon, who won the year's first major at the ANA Inspiration, made a smooth start with a tidy 69.
Co-leader Choi was particularly pleased with her score after only one practice round, leaning heavily on her father-caddie Ji for advice.
"I played just 18 holes before the tournament, so I don't remember every hole," said Choi, winner of one LPGA event.
"But I ask my dad, every hole, every shot and my shots were very good today."
Not that her father's advice was perfect.
"My father missed a couple of shots today but it just happens because wind is every time switching, so very difficult for the caddie," she said.
Former child prodigy Michelle Wie continued her recent resurgence, a fine approach to the ninth hole leading to a birdie, which got her back to even par and set her up for a strong back nine.
"Yeah, 2016 was a miserable year," said the 27-year-old from Hawaii, who has finished in the top four in her past three starts.
"I was sick of playing bad golf, sick of being down and started this year with a really good sense of determination and motivation."
Wie also has adopted a most unusual approach to putting, using several different grips, seemingly on a whim.
So how many grips does she use?
"I don't know," she said. "Don't try to figure it out. I'm like 'this feels right' and I just go with it."