Hewitt, who was the number one ranked player in the world in 2001, is seeking his 29th career singles title. His last win came three years ago in Halle.
The 17-year-old Keys beat Mallory Burdette 7-5, 6-3 in the women's final on Sunday, while Williams defeated Tim Smyczek 7-6 (4), 5-7, 6-3, 6-3 in the men's final.
Someday, the fans will crowd into Arthur Ashe Stadium to watch some other American star play.