Already an LPGA major champion, Henderson became the first Canadian woman in 45 years to win national golf title after winning the CP Women's Open last month.
Amy Olson blitzed the Evian-les-Bains course for seven birdies in a 64 which gave her the early clubhouse lead on eight under, a score later matched by Mi Hyang Lee (66), former British Open champion Mo Martin (66) and Puerto Rican Maria Torres, who hit back from a bogey-bogey start to salvage a 69.
Lee, a two time victor on the LPGA Tour, eagled her final hole to join the lead while Martin, a former Women's British Open victor, stormed home with a final nine 31.
"My long game was really good today", Hall said.
Canada's Brooke Henderson is two strokes back at the halfway mark of the Evian Championship, the final major of the LPGA Tour season.
"I had it in my head as well that I wanted to be bogey-free, and that's quite a special thing round this golf course".
Torres had shared the overnight lead with Spain's Carlota Ciganda, who sits along in fifth place after a round of 70. She missed the cut at 10 over in her only previous major, the Women's PGA Championship won in July by the South Korean world No. 1 Sung Hyun Park, who won't play this weekend.
Lee made an eagle at her final hole, the par-5 ninth, to be the highest ranked co-leader, at No 59.
Austin Ernst (70) is also two shots back, completing her round minutes before Hurricane Florence made landfall close to her home state SC.
Georgia Hall, a homegrown British Open champion last month, had a bogey-free 68 to stand in a big group on 3 under which included seven-time major victor Inbee Park of South Korea. "It's more flooding (risk) where I am".
American amateur Rachel Heck, who is only 16, made the cut at her second major.
"I'm grateful for all the opportunities we get. because I never thought I was going to make it (through qualifying school)", Torres said.
World No 5 Lexi Thompson plays a shot out of the bunker on day two of the Evian Championship.
Lee's fellow Australian, Katherine Kirk, was unable to repeat her impressive opening day form a round of 73 dropping her back to a share of 30th at 1 under and 1 behind Lee. The 2014 ANA Inspiration victor had also dropped a shot at the 17th.
Florence, now a tropical storm, leaves at least four dead
He said parts of North Carolina had seen storm surges - the bulge of seawater pushed ashore by the hurricane - as high as 10 feet. Meanwhile, Super Typhoon Mangkhut has begun pummelling northern areas of the Philippines carrying wind gusts reaching 270kph.
Gov't to Compensate Firms Hurt by N.Korea Sanctions
South Korean President Moon Jae-in and North Korean leader Kim Jong-un will meet in Pyongyang next week, in their third summit. Pyongyang had long disputed the sea line on the grounds that it was drawn unilaterally by the then-U.S. -led U.N.