Taylor Fritz had to work for nearly three and a half hours to put a local into the US Open final for the first time in more than two decades as he held off Frances Tiafoe 4-6, 7-5, 4-6, 6-4, 6-1.
The Californian will be the first from the host country to play for the title since Andy Roddick won in 2003.
Fritz takes a 1-1 record into the Sunday final against Jannik Sinner, who fell on his left wrist but shook off the potential injury during a semi-final victory over Britain’s Jack Draper.
The American finalist hit 16 aces and broke Tiafoe six times as the semi-final went the distance.
“It’s the reason I do what I do, the reason why I work so hard. I’m in the finals of the US Open,” an emotional Fritz said.
“It’s a dream come true; I’m going to give it everything I possibly have. I know that for a fact.”
Fritz, 26 and ranked 12th on the ATP, has turned his hardcourt game around in New York after early exits in both the Montreal and Cincinnati events last month.
He is the first American to play any Grand Slam final since Roddick a Wimbledon, 2009.
Roddick was on hand at the Ashe stadium for the Fritz win, with the smiling Tiafoe becoming the favourite of the crowd over the course of Friday evening.
Fritz made his move in the final set after breaking in the last game of the fourth to square the contest at two sets each.
Fritz swept into command with three breaks of serve, claiming victory in his first match point after winning 25 of 34 points in the fifth set and eight of the last nine games.
“I felt I wasn’t doing anything wrong – just getting overwhelmed,” Fritz said. “I was freaking out a little bit.
“My coach told me to keep doing what I was doing, accept it was okay and keep making him (Tiafoe) do it. That helped to calm me down.”
He added: “It was a crazy match. A lot of it was just about handling the moment and the pressure.
“He was playing at a very high level in the third and fourth sets. “It was really about just staying in it.
“I fought to stay in it and fought to hold my serve and apply pressure as much as possible.”
A pair of Americans were competing in a Grand Slam semi for the first time since Andre Agassi beat Robby Ginepri here in 2003.