The toughest part for Gauff might have been closing out the victory: She needed six match points to get it done, raucously supported by a loud, partisan crowd that chair umpire Alison Hughes repeatedly implored to quiet down.

After failing to convert one match point while serving for the win at 5-3, then another four in what turned out to be the last game, Gauff got the last chance she would need when she smacked a forehand winner to cap a 40-stroke exchange that was the longest of the contest. Muchova then missed a backhand to end it.

“Some of those points, it was so loud, and I don’t know if my ears are going to be OK,” said Gauff, a 19-year-old from Florida who is the first American teenager to make it to the title match in New York since Serena Williams in 2001.

“I grew up watching this tournament so much, so it means a lot to be in the final. A lot to celebrate,” Gauff said. “But the job is not done, so hopefully you can back me on Saturday.”

Gauff was up by a set and 1-0 in the second when three protesters disrupted play from seats in an upper level of the arena. Two of the people were escorted away relatively quickly after security guards and, eventually, police officers arrived. But it took more time to remove the person glued to the ground.

Both players left the court for part of the delay.

The victory was the 11th in a row for Gauff and the 17th in her past 18 matches, a run that began after a first-round exit at Wimbledon in July. The streak includes the two biggest titles of Gauff’s career — and now she needs one more win to get an even more important championship.

She was the runner-up at the 2022 French Open and now will try to claim her first Grand Slam title.

The No. 6-seeded Gauff will face No. 2 Aryna Sabalenka of Belarus or No. 17 Madison Keys of the U.S. on Saturday.

Sabalenka, who won the Australian Open in January and is guaranteed to move up to No. 1 in the rankings for the first time next week, and Keys, the runner-up at the 2017 U.S. Open, were scheduled to meet in the second semifinal Thursday night.