En route to the runner-up finish in a 7-5, 7-5 loss to an overpowering world No. 2 Aryna Sabalenka, Pegula snapped an undesirable winless record in her six previous major quarter-finals appearances.
The breakthrough on Arthur Ashe Stadium's hard court was a confidence-boosting stepping stone like several others in her career, the American told reporters after the women's final.
"I think I've taken confidence from winning a 250, from winning a 1000, from being able to win another 1000. Multiple ones now. Then to be able to be a Grand Slam finalist, I think that was kind of the last thing for me," Pegula said.
"I made a lot of quarter-finals but can I make a semi? Can I be a contender to actually win a Grand Slam?"
"I lost to girls that pretty much won the tournament every time. I know my level was right there," Pegula said.
After battling an injury this season that forced her to skip Roland Garros, a more relaxed approach to this year's US Open provided a lift.
"I handled the moment a little bit better this year ... with just having maybe a different perspective of 'I had a rough start to the year and I didn't really expect to be doing this well in the hard-court swing.'"
"I was able to kind of flip that script."
Pegula's dream run in New York, which will lift her to a career-high-matching No. 3 in the world, spotlights an embarrassment of riches for American women's tennis.
Compatriot Emma Navarro, who lost to Sabalenka in the semi-final on Thursday, will crack the top-10 while current world No. 3 Coco Gauff, the 2023 US Open champion, will only drop a few places after a lackluster showing this year.