Green posted four birdies, three of them coming on the par-5s, in a bogey-free first round.

The West Australian was hot with the putter, beginning with a 15-foot par putt that was followed by a birdie from 20 feet on the next hole.

And she kept it rolling through rain, wind and sunshine despite not having any wet weather gear when she teed off because rain pants "make too much noise."

Green hit only nine greens but took only 23 putts, none of them from tap-in range.

"I guess I just had a lot of luck today with putts going in and getting good bounces," Green said.

"I don't really think I ever had a tap-in putt for my par putts when I missed the green. I made all of them. Very happy with that."

In one of the shots of the day, the 22-year-old holed out from the bunker on the par-5 7th for birdie.

She had another birdie opportunity on the 9th hole, her last hole, but narrowly missed to remain one shot in front of Hyo Joo Kim and Mel Reid.

Green had her own cheering section.

Karrie Webb, Australia's most prolific major champion, has been offering scholarships to two amateurs for the last several years.

They are with Webb this week, and followed Green along. They're all staying in the same house, cooking and working on a 2,000-piece puzzle they wanted to finish in time for their barbecue on Saturday.

This is meaningful to Green because she was a Karrie Webb scholarship winner four years ago, coming over to America for the US Women's Open – the first golf tournament she saw as a spectator.

She even toured the media centre and there she was Thursday evening answering questions about her round.

"That was a real eye-opener for me, and I guess it's pretty cool now to be doing that today," Green said.

RIGHT: Michelle Wie was in tears after shooting 84 in her return from injury. PHOTO: Stacy Revere/Getty Images.

Hazeltine was so long and tough that only 16 players broke par.

There were 20 rounds of 80 or higher, including Michelle Wie, who matched a career high with an 84.

One shot behind Kim and Reid in a tie for fourth are Amy Yang, defending champion and former World No.1 Sung Hyun Park, In-Kyung Kim, Ariya Jutanugarn, Annie Park and Xi Yu Lin.

World No.3 Minjee Lee, who is hoping to snare an elusive first major and possibly the world's top women's ranking, made a slow start.

Lee shot a two-over-par 72 to be tied 46th, after mixing two birdies with four bogeys, to join compatriot Su Oh.

Fellow Australians Webb (five over), Katherine Kirk (six over), Sarah Kemp (seven over) and Wendy Doolan (14 over) made poor starts.

Five-time LPGA winner and former US Women's Open champion Wie, returning to competition from injury, was in tears.

"It's hard," Wie said. "It's just one of those situations where I'm not entirely sure how much I have left in me."