The 26-year-old, who has produced rounds of 64 on either side of a 69 on Friday, began and finished strongly to move to 16-under and put distance between herself and the chasing pack heading into the final round.
Lexi Thompson and Kris Tamulis are next best on 12-under after carding rounds of 68 and 67 respectively, with a group of six players a further two shots back.
World number one Inbee Park finds herself seven shots adrift after a third round of 66.
One of three overnight co-leaders, Salas birdied three of the first four holes to edge ahead, with a further birdie at the ninth seeing her take the turn in 32. Three birdies in a row from the 14th to the 16th ensured she would finish well and stay ahead of the pack after a superb bogey-free round.
Tamulis began with a birdie at the first, but a bogey just before the turn saw her return to level par for the day. However, three birdies in four holes after the turn saw the American gain momentum. A further birdie at the 17th saw Tamulis enter the clubhouse on five-under for the day after a round of 67.
Thompson had held a share of the overnight lead with Salas and Alison Lee, but was unable to get her round going on Saturday, registering four birdies and a bogey at a time when many around her were finding scoring easier.
Caroline Masson was a late mover on the day, birding three of the last four holes in a round of 65 which took her to 10-under, a mark she shares with Brittany Lincicome (65), Alison Lee (70), Gerina Piller (69), Katie Burnett (66), and Ryu So-yeon (65).