SAN MARTIN, Calif. — When Mirim Lee walked off the course following her record-tying round, she described her day with words usually not heard when talking about the U.S. Women’s Open.

“So today’s round was easy day – easy round, yeah,” Lee said.

She sure made it look that way when she became the fifth golfer to shoot a round of 8-under par at the U.S. Women’s Open on Thursday, making 10 birdies on the way to a 64 to take the first-round lead at CordeValle.

With the greens not quite as firm as they likely will be later in the week and the wind not playing a major factor, there were low scores to be had throughout the field – at least for the opening morning of the tournament when 23 players shot under par, including six of the top seven on the leaderboard.

“I definitely expect it to change,” said Cristie Kerr, who was three shots behind Lee in a tie for second. “I don’t think the USGA likes when we shoot 8 under on their golf course. You have to expect it to change and if it doesn’t, then you’ll have opportunities to score.”

The play got much tougher in the afternoon when the wind picked up and only 14 players were under par, led by Amy Yang, who birdied 18 to move into a three-way tie for second at 5 under with Kerr and Minjee Lee.

None of the players in the marquee group that featured three of the top four players in the world in Lydia Ko, Brooke Henderson and Lexi Thompson could break par. Ko birdied her final hole at No. 9 to finish the day 1 over, one shot ahead of Thompson and three in front of Henderson.

Those three will need to do plenty of work to catch Lee.

“I don’t know what course she played, maybe the ladies tees, maybe a different course,” Ko said. “But she played fantastic.”

Lee is the first woman to shoot that much below par at the U.S. Open since Lorie Kane and Becky Iverson did it in the second round in 1999 at Old Waverly in Mississippi. The lowest total score in a round in U.S. Open history is a 63 by Helen Alfredsson in 1994 at the par-71 Indianwood in Michigan.

Lee capped her record day with a birdie from about 8 feet on her final hole at the par-5 ninth.

“The course is perfect now,” Mirim Lee said. “Greens are really fast.”

EUROPEAN TOUR: Scott Hend of Australia and Felipe Aguilar of Chile made it through blustery conditions and shot 3-under 69 to share the lead after the first round of the Aberdeen Asset Management Scottish Open at Inverness, Scotland.

Phil Mickelson wasn’t so fortunate. The five-time major champion, a winner the last time the Scottish Open was held at Castle Stuart, made three bogeys on the par 5s and opened with a 76.