Henderson had four birdies in a seven-hole stretch and closed with three pars on the gusty Ocean Club layout. The 20-year-old Canadian has five LPGA Tour victories, winning last year in Michigan and New Zealand.
Australia’s Sarah Jane Smith finished with a bogey to drop into a tie for second with Spanish rookie Luna Sobron Galmes. Top-ranked Shanshan Feng birdied her last for a 70, matching Danielle Kang, Lindsey Weaver, Katherine Kirk, Jing Yan and Maria Torres, the tour’s first player from Puerto Rico. Kang played alongside Henderson and I.K. Kim.
Lexi Thompson, a playoff loser to Brittany Lincicome last year, opened with a 72. Michelle Wie eagled the par-5 11th in a 73, and playing partners Lincicome and third-ranked So Yeon Ryu followed at 74.
Kim and Ariya Jutanugarn shot 76, and Stacy Lewis had two double bogeys in a 78.