Jaye Marie Green and Wei-Ling Hsu of Chinese Taipei fired rounds of 65 at the Blythefield Country Club to sit one stroke back.
However, world number one Inbee Park did not enjoy the best of days as she is currently in a tie for 37th following a first-round 70.
Salas, who is looking to win her second LPGA title, was the one of the leaders to have a bogey-free round, making five birdies and an eagle at the par-five 11th.
Kirk, who started on the ninth tee, began her round strongly with two birdies and an eagle on her first four holes. After registering a bogey at the 15th, she bounced back with birdies at the 16th and 17th to round off her front nine.
Her good run of form continued onto her closing nine where she made two more birdies – at the first and fifth – before faltering with her second bogey of the round at the seventh. But, she finished her round on a high with a birdie at the eighth.
Carter meanwhile enjoyed a superb front nine that produced five birdies, including three in a row from the fourth to the sixth hole. Even though the back nine did not prove to be as successful, she still managed three more birdies and a bogey.
Green and Hsu both sit one shot behind Salas, Kirk and Carter after they each made eight birdies and two bogeys during their respective rounds of 65s.
Jane Rah, Ilhee Lee, Q Baek and Kris Tamulis are in a tie for sixth and two strokes behind Salas, Kirk and Carter after carding first-round 66s.
After starting solidly with two birdies on her opening nine holes, Park endured a turbulent back nine. The world number one, who had begun the day on the ninth tee, sinking a birdie at the first before stumbling with consecutive bogeys at the second and third. She would go on to register a birdie at the eighth, but finished her round with a bogey at the ninth.