'I never won a tournament by more than a shot. I feel like I have reached a new level in my game,' said Kerr, who pocketed $330,000 for the win. 'To know that you can play that well and beat the best players in the world, perhaps be one of the best players in the world is a great feeling.'
'I think I reached a little bit more of a, not a physical different level of my game, but maybe a mental higher level of my game,' said Kerr. 'It was really a test for everybody.'
McGill also posted a 1-over 72 for her four-round total of 3-under-par 281. The solo second matched her best finish on the LPGA Tour.
Annika Sorenstam never got on track on Sunday in her quest for another LPGA Tour record. If she could have visited the winner's circle, she would have won six consecutive events, which would have been a new tour mark.
However things did not go well for the top player in the game. She opened with a 5-over 76, but crept back into the event with a 67-69 in rounds two and three.
Sorenstam shot a 3-over 74 in the final round to tie for 12th place at 2-over-par 286.
'I am disappointed, there is no doubt about it,' said Sorenstam, who finished over par in a tournament for the first time since the John Q. Hammons Hotel Classic in September of 2003. 'I had a great opportunity to do something, I just didn't do it. I just have to start over and maybe I can do another streak. We'll see what happens.'
Instead it was Kerr, who picked up her first win of 2005 and her fifth overall on the LPGA Tour.
Kerr started the final round with four-shot lead over McGill and was never threatened on Sunday.
She dropped a shot to par at the second hole, but rebounded with a 3-foot birdie putt at the par-5 third. Kerr tallied another bogey at the sixth, and one more at No. 10, but her advantage only fell to four shots.
At the 11th, Kerr ran home a 7-footer for birdie to extend her lead to five. McGill got one closer with a 20-foot birdie putt at the 14th, but Kerr had an answer for that.
Kerr's second landed in a bunker at the par-5 15th, but she blasted out to 6 feet. She drained the birdie putt to reclaim her five-stroke advantage over McGill.
Kerr made a mess of the 18th off the tee with a terrible drive that forced the 27-year-old to lay up with her second. She ended up with a bogey, but it didn't matter.
'Sometimes when you make bogeys you feel it slipping away. I didn't let that happen mentally today,' said Kerr. 'I was getting mad at myself. I wanted to shoot under par today and it didn't happen.'
Natalie Gulbis posted a 2-over 73 in the final round and tied for third place with Catriona Matthew (71) and Michele Redman (70). The trio came in at 2-under-par 282.
Gloria Park (69) and A.J. Eathorne (70) tied for sixth place at minus-1.
Juli Inkster (71), Rosie Jones (69), Mi Hyun Kim (73) and Shi Hyun Ahn (73) tied for eighth place at 1-over-par 289.