Taylor Dent and Robby Ginepri will contest the first all-American final in Indianapolis since Pete Sampras beat Jim Courier 13 years ago.
The unseeded Ginepri went through when he followed up his win over holder Andy Roddick by recording a 5-7, 6-2, 6-3 victory over Slovak Karol Beck in the semi-finals of the RCA Championship on Saturday.
Later in the day, fourth seed Dent defeated seventh-seeded Briton Greg Rusedski 6-4, 6-4.
Ginepri, who won his only previous title in Newport two years ago, fired seven aces against 14 for 10th seed Beck.
The American lost the last game of a rain-interrupted opening set but recovered in the second by twice breaking serve.
Ginepri broke serve twice more in the third set to clinch victory.
"I served better on Friday but I got in a couple of good returns when I broke him in the third set," he told reporters.
"I wasn't thinking about beating Andy, I just focused on one point at a time. Good things happen when I stay positive and mentally tough."
Dent won his serve and volley contest with Rusedski in 70 minutes, hitting 14 aces and committing only nine unforced errors.
"My level was very high today," said the world number 30, who has not dropped a set all week.
"I was very solid, I only hit one or two bad volleys the entire match."
Rusedski said he was tired following his three-set win over German Nicolas Kiefer on Friday night.
"I did not have time to recover," he said. "After a two and a half hour match, I got to bed at 2am.
"It was tough to play today. Taylor just played better than I did. I could not move like I wanted."