Lee, an LPGA Tour rookie, made seven straight birdies in the middle of the round, and leads Christina Kim and Jenna Daniels, who both shot 6-under 66 to tie for second place.
"I woke up this morning tired from a long week of traveling," said Lee. "I bogeyed the second and I said to myself, 'Okay this week's going to be tougher.' Then obviously I had a great round."
Daniels made double-bogey on her final hole to drop into a share of second place with Kim.
Morgan Pressel opened with a 4-under 68 and is joined in fifth place by Cathy Johnston-Forbes, Joo Mi Kim, 1998 champion Danielle Ammaccapane, Tina Barrett, Emily Bastel, Dawn Coe-Jones, Mhairi McKay, Diana Ramage, Kim Saiki and Sherri Turner.