The title moved her from 80th to No. 44.
Thompson became the youngest player to win an LPGA event with a five-stroke victory. The teenager finished at 17-under-par 271.
It was far from a watered-down field that Thompson beat as seven Top 10 players competed at the tournament in Alabama. That doesn't include Stacy Lewis, whose tie for sixth allowed her to move from 11th to 10th in the rankings.
Yani Tseng remains solidly No. 1 in the women's rankings, posting a points average of 16.50. Suzann Pettersen is second at 11.89 and Cristie Kerr (11.71) is third while Choi Na-yeon (9.00) holds the No. 4 spot and Jiyai Shin (8.87) is fifth.
Lewis' average improved to 7.16, edging Kim In-kyung (7.14) for 10th in the rankings. Kim is 11th.