Sweden's Ingrid Lindblad shot a six-under 65, the lowest round by an amateur in the 77-year history of the US Women's Open, and trails leader Harigae by one shot.
"She was fearless," said playing partner Annika Sorenstam, Sweden's most famous female golfer.
Because she's an amateur, Lindblad wouldn't be able to collect the record US$1.8 million ($2.75m) first-place prize if she holds on to win the event. She would have had to declare as a professional before the tournament began.
When asked if, in hindsight, that was a mistake, the 22-year-old LSU junior known to her friends as "Iggy" paused and said with a smile, "I'm going to stay in college for like another year or so".
"But when you say it, yeah ... it would have been fun to win a little bit of money."
Harigae has 19 career top 10s on the LPGA Tour but this is the first time she's led a tournament.
She shot 30 on the front nine and surged ahead of Lindblad with birdie on the par-3 16th hole on a heat-drenched afternoon that drove some spectators to the exits early.
Harigae, who played one year at Duke before turning pro, said she was thrilled to be back in North Carolina, joking that she drew inspiration from six-time NBA champion Michael Jordan, who played for the Tar Heels.
"Obviously, being a big Jordan fan, so just kind of like going off the Jordan vibes," Harigae said. "Must be the shoes, right?"
On the PGA Tour, Kiwi Danny Lee finished his first round of the Memorial Tournament in Ohio with a one-over 73 to sit six shots behind the leaders.
Lee went birdie, bogey, birdie, bogey to start his round before a run of pars to finish off his first nine. He would go on to birdie the 11th and 14th but ended poorly with three-straight bogeys.
Six players sit in a tie for the lead at five-under: Cameron Young, Luke List, Cameron Smith, K.H. Lee, Mackenzie Hughes and Davis Riley.
- With AP
