Second seed Garbine Muguruza claimed her second title of the year after recovering from a set down to win the inaugural Chicago Fall Classic.
The Spanish former world number one came through 3-6 6-3 6-0 against Ons Jabeur of Tunisia, the sixth seed.
Muguruza was outplayed in the first set and then lost her serve twice early in the second to be in real trouble.
But she managed to regroup and as she got stronger, Jabeur, the world number 16, started to struggle.
Muguruza reached the final after a walkover in her semi-final when Czech Marketa Vondrousova, the Tokyo Olympic runner-up, pulled out with an injury.
Jabeur's semi-final on Saturday ended early when Kazakhstan's fifth-seeded Elena Rybakina retired with the Tunisian leading 6-4 3-2.
Earlier on Sunday, Italy's Jannik Sinner swept past French veteran Gael Monfils to successfully defend his Sofia Open crown and boost his chances of reaching next month's ATP Finals.
The 20-year-old top seed won 6-3 6-4 for his fourth career title.
The win will see him move into 10th place in the race for the eight-man season finale which will be held in Turin, Italy from 14 November.