Gulbis was joined atop the leaderboard at Wykagyl Country Club by Beth Bauer and 2003 champion Hee-Won Han, who is a four-time winner on the LPGA Tour.
Nancy Scranton posted a 2-under-par 69. She was joined in a tie for fourth place by Kim Saiki, Teresa Lu and Allison Hanna. Soo Young Yoo is also at minus-2 through 17 holes.
Women's world No. 1 Annika Sorenstam and defending champion Paula Creamer share 24th place at 1-over-par 72.
Sorenstam, coming off her first missed cut since 2002, opened on the back nine and bogeyed No. 11. She moved to 1 under thanks to birdies at 13 and 15. After nine straight pars, the Swede bogeyed Nos. 7 and 8 to drop to plus-1.
'I thought I played well. It was very difficult, very, very difficult,' admitted Sorenstam. 'I hit a lot of good shots. It would have been nice if I converted. I thought I played really, really good, but just had two bogeys in the end.'
Creamer was 5 over par through 11 holes after a bogey and two double bogeys. The 19-year-old birdied three of the next four holes, then closed with a birdie at the 18th to end at plus-1.
Gulbis struggled out of the gate with bogeys on two and four. She recovered those lost strokes in remarkable fashion as she holed a wedge shot for eagle on the par-4 eighth.
'I three-putted for bogey on four and had missed a green at the second, then I holed out on No. 8 with a wedge,' Gulbis stated. 'That changed my momentum and I played well on the back nine.'
Around the turn, Gulbis used that momentum to birdie the par-4 10th to move to minus-1. The 23-year-old parred her next four holes.
Gulbis collected her next birdie on No. 15. She made it two straight to get to 3 under. However, she stumbled to a bogey at the 17th. Gulbis recovered that lost stroke with a birdie on the last to gain a share of the lead.
'It definitely got windy today,' Gulbis admitted. 'It was not crazy, but it was tough. The rough is up too.'
Han, who was a playoff loser in 2002 along with her win here in 2003, jumped out of the gate with birdies on one and three. She cruised to 10 consecutive pars from there.
The Korean moved to 3 under with a birdie at 14. Han tripped to a bogey on 16, but came right back to birdie the 17th to end at 3 under.
'The key was I actually had pretty good shots today,' said Han. 'I had a couple birdie putts that I made.'
Bauer started her round with five straight pars. She posted back-to-back birdies from the sixth. Bauer claimed the lead at 4 under with birdies at the 10th and 14th. However, she stumbled to a bogey on the par-three 16th to end at minus-3.
Mi Hyun Kim shares ninth place at 1-under-par 70 with Marilyn Lovander, Louise Stahle, Heather Young and Seon-Hwa Lee.