HARRISON, 12 Jun 2015 (AFP) - Canadian 17-year-old Brooke Henderson was alone in second on 67, a bogey at her final hole -- the par-five ninth -- the only blemish on a card that included five birdies and an eagle.
Australian Hall of Famer Karrie Webb, Thailand's Moriya Jutanugarn and England's Charley Hull shared third on 68.
Like Henderson, Webb -- more than twice her age at 40 -- also teed off on 10 on the par-73 Westchester Country Club course and moved as low as six-under before her only bogey of the day at the par-four seventh.
It was a further stroke back to France's Karine Icher and China's Feng Simin on 69.
South Korean Park In-Bee, the two-time defending champion of the tournament formerly known as the LPGA Championship, was among a big group on 71.
In addition to seeking a third straight title in the event, Park is closing in on the world number one spot occupied by 18-year-old New Zealander Lydia Ko, who fired a first-round 72.
Leading first-round scores on Thursday in the Women's PGA Championship, the second major of the 2015 LPGA season (USA unless noted, par-73):
66 - Jenny Shin (KOR)
67 - Brooke M. Henderson (CAN)
68 - Karrie Webb (AUS), Moriya Jutanugarn (THA), Charley Hull (ENG)
69 - Karine Icher (FRA), Feng Simin (CHN)
70 - Joanna Klatten (FRA), Chella Choi (KOR), Lee Min (TPE), Kim Hyo-Joo (KOR), Sandra Gal (GER), Jane Rah, Kim Sei-Young (KOR), Cristie Kerr, Jessica Korda, Brittany Lincicome, Lexi Thompson, Candie Kung (TPE), Azahara Munoz (ESP), Jennifer Song, Stacy Lewis
71 - Brittany Lang, Yan Jing (CHN), Gwladys Nocera (FRA), Paula Reto (RSA), Park In-Bee (KOR), Christina Kim, Kris Tamulis, Sophia Popov (GER), Sydnee Michaels, Mina Harigae, Paula Creamer, Anna Nordqvist (SWE), Perrine Delacour (FRA), Hur Mi-Jung (KOR), Caroline Hedwall (SWE), Pernilla Lindberg (SWE), Kelly Shon