The notorious Erin Hills club may be largely devoid of trees but it was the lush rough and course's challenging contours that had the world's best players scratching their heads on Thursday (Friday AEST).

By the end, Americans Angel Yin and Yealimi Noh, South Koreans A Lim Kim and Jin Hee Im, Japan's Rio Takeda and Spaniard Julia Lopez Ramirez were in a six-way tie for the first-round lead after all fired four-under-par 68s.  

No Australians managed to shoot under par at the season's second major championship, which carries a $US2.4 million ($A3.7m) winner's cheque out of the $US12million ($A18.6m) total purse.

But as Yin said, "you can't win the tournament on Thursday but you can shoot yourself out of it".

Hannah Green appeared to be heading that way after racking up a wretched double-bogey seven at the 7th, her third-last hole of the day after teeing off on No.10.

But the world No.8 rallied with birdies at her final two holes to claw her way back to even par.

Green, Kim and American world No.1 Nelly Korda were among 24 players to post rounds of 72.

Playing in one of last groups of the day, Kim bogeyed the last but knows she's right in the thick of it if she hangs tough.

"Didn't get anything going but, then again I, I knew that pars were good out here," she said.

"It is a major. The roughs are up, you just want to hit fairways and greens and try to make the most putts as you can.

"Obviously finished quite late so the greens can be a little bit bumpy and it was raining yesterday, so it was soft so just tried really hard to stay patient out there.

"Just knowing my game's good enough to have good rounds so I just push though with lots of confidence building tomorrow and hopefully I can make the most of the morning tee time."

Green carved out her 72 in the complete opposite manner to steady Kim and Korda, who collected her lone birdie of a frustrating day at the par-5 last.

Green mixed three bogeys and that double with five birdies, including four on the back nine to earn her way into a share of 34th spot.

Minjee Lee is one stroke further back after struggling to find her groove, even with the gallery support of the legendary Karrie Webb.

Webb is in town to mark 25 years since Australia's most prolific ever major winner went back to back at the U.S Open in 2000-01 and figured she'd follow Lee around.   

Gabriela Ruffels also carded a one-over 73, but remains in the hunt only five shots behind the leaders.

Steph Kyriacou opened with a 74, while Jennifer Elliott has a mountain to climb to make the halfway cut on her major championship debut after starting with a six-over 78 to be tied for 132nd in the 156-player field.