Top seeded and defending champ Serena Williams destroyed Sorana Cirstea 6-1, 6-2 in one hour to reach her second straight final at the WTA hardcourt tournament at Stanford.
The first all-American final on US soil since 2004 will feature top seed Williams against Californian Coco Vandeweghe, a lucky loser from qualifying who defeated fifth seed Yanina Wickmayer 6-2, 3-6, 6-2 to reach the first WTA final of her career.
Vandeweghe got into the main draw after a withdrawal and made the most of her opportunity, beating former world number one Jelena Jankovic in the second round.
Williams had a poor first serve percentage of 37 percent but did not waste time in crushing Cirstea to reach her second final in a week after winning Wimbledon seven days ago.
The Romanian was saddled with 31 unforced errors and got only one break point chance against Williams.
The 30-year-old Williams is poised to join sister Venus on 43 career trophies if she can win another title against her 120th-ranked opponent.
Williams played this week fighting jet-lag after flying over directly from Wimbledon eight time zones away.
"This week was weird," said the 14-time grand slam champion. "I felt like I wasn't there for about half of it, but here it is, Sunday and another final."
Williams finished on her second match point after Cirstea saved a first winning chance a game earlier.
"It took me awhile to figure out her game," Williams said. "I had to wait her out. She hits really hard, but I did well."
Vandeweghe, 21, and coached this week by her mother, will rise to around 75th as a result of her success here, according to the WTA Tour.
She hammered a dozen aces and broke experienced Belgian Wickmayer four times in the match which lasted just over two hours.
At one tense moment Wickmayer drew a warning for swearing.
Vandeweghe said she was furious with herself when she crashed out of qualifying.
"I had a bad tennis day and paid for it," she said. "But once I got into the main draw, I took advantage of my opportunities.
"I stuck with my game plan, I served big and returned well this week. When my game comes together like that I can play well from the baseline.
"I'm just so excited to be in the final."
Vandeweghe's surprise showing this week by far surpassed her previous career bests: quarter-final appearances in her native San Diego and Tokyo two years ago and at Memphis in 2011.
She was the second lucky loser to advance to the WTA semi-finals this season after France's Mathilde Johansson in Fes, Morocco. The last one to reach a final was Hungarian Melinda Czink at Canberra five years ago.
The last all-American WTA final occurred eight years ago when Serena played her sister Venus at the year-end WTA Championships.
The top seed will have the massive experience edge when she takes on Vandeweghe.
"She will have nothing to lose and those are the type of players who can be the most dangerous," said Williams. "I've got to do more in the final than I did today. But I'm just glad to be playing for another title."