Maguire, 26, is trying to become the first Irish winner in LPGA Tour history.
“There is not really time to look around or even look behind.
After rain and thunderstorms delayed the start two hours, Maguire birdied five her first nine holes, bogeyed Nos.
“Then, I actually holed a bomb on 2, I think, like 60 feet.
“The greens were definitely a lot softer today so you could be more aggressive,” Korda said after her morning round.
Brooke Henderson, the winner in 2017 and 2019 in the event that was canceled last year, missed the cut by a stroke after rounds of 75 and 67.