Hjorth, whose European team lost to the U.S. in the ninth Solheim Cup last week, established a new course record for the tournament with her 64. She collected seven birdies and an eagle and dropped just two shots on the day.
'I played really solid and had a lot of birdie chances,' said the 31-year-old, who lost to American Natalie Gulbis in the Solheim Cup singles on Sunday. 'Some went in and some didn't.'
Hjorth leads Michelle Ellis and Karine Icher by one stroke at Cedar Ridge Country Club. Defending champion Annika Sorenstam, a two-time winner here and also a European Solheim Cupper, is tied for fourth place at minus-3 with Rachel Hetherington and Diana D'Alessio.
Sorenstam played her first nine holes -- the back nine -- at 1 over par before lighting up the front nine with red numbers. She was plus-2 after a bogey at No. 1, but a string of three straight birdies got her going, and she finished with six total on the outward nine.
'It is interesting, it is,' Sorenstam joked of her slow start and strong finish. 'The back nine was interesting for me...let's put it this way -- obviously I'm very glad to finish 3 under, especially after I was 2 over after 10 holes.'
Ellis' round was less up-and-down. She opened on the front nine with birdies on three of her first five holes, and dropped her only shot at the par-4 eighth. Consecutive birdies at Nos. 13 and 14 saw the 29-year-old reach minus-4 and sole possession of the lead.
'I'm obviously excited. It's been a bit of time since I put a first round together,' said Ellis, who struggled with a rib injury after the U.S. Women's Open in June. 'Everything is starting to come back together slowly...I'm starting to get back in the swing of things and get back in the hunt and get used to being in that position again.'
Icher began her bogey-free round on the back nine and reached minus-2 with her first two birdies of the round at 10 and 14. Her steady play continued with seven pars on the front nine to go along with birdies at the first and fifth.
'I'm really happy about my round today,' the 26-year-old said after joining Ellis for the clubhouse lead. 'I didn't have any bogeys, so when you play a round without bogeys, it's always nice. And it's a very tough course, so I'm pretty happy to make this score today on this course, and I hope the same for tomorrow.'
Nineteen-year-old rookie Paula Creamer, who played in her first Solheim Cup last week for the U.S., is tied for seventh place at 2-under-par 69. She is joined there by Kris Tamulis and Mi Hyun Kim.