Webb stands at 13-under-par 200 through three rounds, five shots ahead of Lorena Ochoa, Pat Hurst and defending champion Cristie Kerr. Her lead moved from three shots to five shots when Hurst double bogeyed the 18th hole.
Hee-Won Han is alone in fifth place at 6-under after a 69, and Jeong Jang is one shot further back in sixth following her second consecutive 70.
Reigning Rookie of the Year Paul Creamer fired a 4-under 67 and leads a group of four players tied for seventh place at minus-4. She was joined by Yu Ping Lin (67), Angela Stanford (70) and Joo Mi Kim (70).
Webb, who has held the lead after all three rounds, sits atop the leaderboard after 54 holes for the 26th time in her LPGA Tour career.
Although she has won 16 previous times in this position, the last time Webb held the third-round lead was four years ago at the 2002 Jamie Farr Kroger Classic, where she tied for third.
Webb has already clinched a berth in the season-ending ADT Championship by way of her playoff win over Ochoa at the Kraft Nabisco Championship. The winner of this tournament is also awarded an automatic berth, so if Webb is victorious again, she will remain the only player qualified for the ADT.