Pressel took advantage of the favourable afternoon conditions as she birdied two out of her first three holes before finishing with her fifth birdie of the round on the par-five 18th.
Even though she sits four strokes behind Pressel on the leaderboard, world number one Lydia Ko achieved an amazing personal feat as she matched Hall of Famer, Annika Sorenstam's streak of 29 consecutive rounds under par on the circuit.
Ko finished with a first round 71 after struggling in the windy conditions on her front nine.
Sitting alone in second place is Japan's Ai Miyazato, who registered a first round 68 and is looking to become the first Japanese woman to win the tournament.
Gwladys Nocera, So Yeon Ryu, Alison Walshe and 54-year-old Juli Inkster all sit one shot behind Miyazato in third place.
Meanwhile, reigning champion Lexi Thompson hit a first round 72, while Michelle Wie recorded a 73 and world number two Inbee Park carded a 74 in the first women's Major of the season.