Hjorth led by herself after round one and shared the lead after two rounds. She stands at 14-under-par 202 through three rounds.
Seon-Hwa Lee (69) and Il Mi Chung (70) share second place at minus-13.
Cristie Kerr, who shared the lead with Hjorth after two rounds, managed an even-par 72 in the third round. She is tied for fifth at 12-under-par 204 with Nancy Scranton, who carded nine birdies en route to a 9-under 63. Kyeong Bae is alone in sixth at minus-11 after a 68.
Lorena Ochoa, the LPGA Tour's leading money winner, shot 70, while women's world No. 1 Annika Sorenstam posted a 69. They are tied for ninth at 9-under-par 207.
Hjorth opened with a 12-foot birdie putt on the second to move one ahead of Kerr. She then two-putted for birdie on the fourth, her third birdie in three rounds on that hole, to remain one up on Kerr, who also birdied No. 4 at The Rail Golf Course.
The Swede stumbled to a three-putt bogey on the seventh for the second round in a row. However, Hjorth bounced back with a birdie on the eighth. She parred three in a row around the turn.
Hjorth dropped another stroke on the par-5 12th. She recovered that lost stroke with a birdie on 14. The two-time winner on the LPGA Tour parred the last four holes.
'I have been waiting to hit a lot of good drives,' admitted Hjorth, whose two wins came in 1999. 'I hit a lot of good drives today, but unfortunately I didn't hit my approach shots as close as I would have liked. That was the difference. I'm happy with today's round though.'
Lee birdied the fourth and fifth, each for the third straight round, to move to minus-12. She tripped to a bogey at the 14th, but came back to birdie 15 and 17 to get within one of Hjorth's lead.
'I played well today. My putting was great,' Lee stated. 'I think the up and down I made on No. 9, that helped a lot.'
Chung opened with a bogey at No. 1. She parred her next eight holes to turn in 10 under. She birdied the 10th from 15 feet out, but gave that stroke right back with a bogey on 11.
The 34-year-old Korean drained a 20-foot eagle putt on the par-5 15th to jump to 12-under. She move into a share of second with a birdie on the 18th.
'Today's round was very long. I couldn't wait until it was over,' said Chung. 'Obviously that eagle (on No. 15) was the turning point of my round. I was having such a hard day, but when it went in and there were only three holes left, I thought there may be some chance that I can probably catch up.'
Lindsey Wright fired a 5-under 67 to move into a tie for seventh at 10-under-par 206. She is tied with Nina Reis (72).
Brittany Lang and Angela Stanford stand alongside Ochoa and Sorenstam at minus-9.