Amanda Anisimova moved into the fourth round of Wimbledon for the first time as she fought back from a set down to beat fellow American Coco Gauff.
Anisimova, 20, was playing on Centre Court for the first time and gained a 6-7 (4-7) 6-2 6-1 victory over the 18-year-old French Open runner-up.
It means Anisimova, the 20th seed, has reached the last 16 of all three Grand Slam tournaments this year.
Gauff was the 11th seed and failed to reach round four for the first time.
Anisimova told BBC Sport: "This is the most special day of my career. It's just a huge privilege to play on this court playing Coco.
"She's an amazing player, got to the final of a Grand Slam so I wanted to soak up the moment. Winning is so special, especially in front of a full crowd.
"The worst thing for a tennis player is to lose 7-6 in the first set. I had the same experience in the French Open, but it's important to bounce back and give everything you have.
"Although it was extremely exhausting, I pushed through and was so happy to get the win."
Anisimova will next play France's Harmony Tan, ranked 115th.
However, Tan has been in great form in these Championships. She defeated seven-time Wimbledon champion Serena Williams in round one, eliminated Spain's 32nd seed Sara Sorribes Tormo in the second round and thrashed Britain's Katie Boulter 6-1 6-1 earlier on Saturday.
Anisimova made a nervous start on Centre Court, losing the opening three games, although she then won four in a row and was a break up before Gauff fought back to force the tie-break.
Despite holding a 4-1 lead in the tie-break, Anisimova, who made 26 unforced errors in the opening set, fell a set behind.
However, she showed great strength of character as she drastically reduced her mistakes and began to take control. She clinched the second set, breaking Gauff's serve to love in the eighth game and then dominated the final set.
Anisimova and Gauff had been two of the four Americans to reach the third round of the women's singles, while eight players from the United States were in the last 32 in the men's singles.
"There are so many American players doing well and I'm proud of my country and how we have been doing," added Anisimova. "It was really exciting to have an all-American clash on this court so it was really special."