Park, who also had led after Friday's round, used a birdie on the final hole to become the only player in the field to break par at Sebonack Golf Club Saturday, finishing with a comfortable lead at 10-under-par 206.
Park, who has already won each of the LPGA season's first two majors, is looking to become only the second player in history to take three in a row to start a season.
She is also seeking her sixth triumph of the year overall.
Her closest competitor is I.K. Kim, who carded a 1-over 73 to finish 54 holes at minus-6.
Alone in third place at 3-under 213 was Jodi Ewart Shadoff, who posted a 2-over 74.
Angela Stanford (74) and So Yeon Ryu (73) were knotted for fourth at minus-1.
Ha-Neul Kim, who led after the first round with a 66, has fallen into a five-way tie for 20th place at 5-over after posting a 77 Friday and 78 Saturday.