Lincicome leads by three over Inbee Park and Lexi Thompson with Jane Park, Meena Lee and New Zealander Lydia Ko another shot back.
"It's been incredible," Lincicome said of her first two rounds. "I haven't been here in a while so it's pretty exciting anytime you can shoot under par especially at a major. It feels really nice.
"I feel like all year I've been doing a lot of good things, hitting well, putting well, chipping well, they just don't seem to all come together on the same day. So it was nice to play the last two days and just kind of seeing like I was out there doing my thing and there was not too much stress involved."
Ko is well enough placed to achieve a lot of milestones this week.
Ko is the only player in LPGA history to win two events as an amateur, the youngest to win an event (15 years, 4 months, 2 days) and became the youngest player to reach $1 million in career earnings this season (17 years, 2 months, 26 days).
The Tour rookie could pick up another youngest title this week with a win and would become the youngest major champion in history (male or female). She'll be 17 years, 3 months, and 24 days on Sunday. But Ko said she has done a good job at concentrating on the task at hand and none of the extra superlatives.
"For me I think about winning at the end of the week," said Ko. "I know especially like Toledo I realized I became a millionaire after that. I mean, to kind of have those accomplishments is really cool, but I'm really going out there and trying to play the best I can. It's hard to control what I do, but to control what other people are doing is pretty much impossible."
Another milestone is also in the offering if she is able to produce something special over the weekend as if she were to win and current number one, Stacey Lewis, finishes outside the top three Ko becomes the world number one. Lewis is in 33rd positon this week.
Sarah Kemp currently leads the Australians in a share of 25th while Karrie Webb and Sarah Jane Smith are 33rd.