That honour went to American Marina Alex, who matched the course record with a 10-under 62 to lead by two from Lee and Canadian Brooke Henderson.

World No.7 Lee opened her round with a five-hole birdie blitz from the 10th to 14th holes, during a round that fetched nine birdies and a lone bogey on her closing par-4 9th.

"I think it was a combination of everything," Lee said. "Most of the day I struck it pretty well with my iron shots.

"I had pretty good control of the yardages and I hit some solid putts."

Compatriot Su Oh was also in blistering form with her six-under-par 66 keeping her firmly in contention in joint-fifth position.

Alex birdied her last four holes to take the lead after the opening round of the 2018 Portland Classic. PHOTO: Jonathan Ferrey/Getty Images.

With Stacy Lewis unable to defend her title as she prepares for the birth of her first child, Alex is using her friend's caddie, Travis Wilson, at Columbia Edgewater.

"It's been a blast," Alex said. "The timing was great. He wanted to work a couple more events before the season ended and I was looking. Trav is awesome. So much fun, really light hearted."

Winless on the tour, the 28-year-old former Vanderbilt player birdied the last four holes and five of the last six in a back-nine 30.

"Got my ball-striking together and it was awesome," Alex said.

Henderson, the 2015 and 2016 winner, birdied five of the last six holes for a 64.

The 20-year-old Canadian star is coming off a victory Sunday in the CP Women's Open on home soil in Saskatchewan.

Women's British Open champion Georgia Hall matched Oh at 66 while Inbee Park, playing for the first time since the Women's British Open, opened with a 69.