Lewis won by six shots over South Korea' s Meena Lee with Michelle Wie one shot further back in 3rd position.
Lewis began the final round tied with Lee but by the time she made the turn in 31 she was five shots clear eventually extending that lead to six to win her 9th LPGA Tour title.
She will advance from 3rd to a very deserved 2nd in the Role World Ranking and is now within striking distance of regaining the world number one position currently held by Inbee Park
Lewis now has career earnings of close to US$7 million and along with now Michelle Wie continues to fly the flag for the Americans on the LPGA Tour.
Stacy Keating only just managed to get a late start in the event but ended up as the leading Australian when she finished tied for 19th.
Sarah Jane Smith was 25th while Sarah Kemp, after a good start to the event, slipped to finish 35th