Morgan's 6yard header, on a long cross from Heather O'Reilly, looped high into the net over goalkeeper Erin McLeod for the winning goal. Megan Rapinoe scored in the 54th and 70th minutes, and Abby Wambach in the 80th for the US.
The Americans overcame three onegoal deficits, all due to a hat trick from Canada's Christine Sinclair, who scored in the 22nd, 67th and 73rd minutes. In many ways the win was reminiscent of the landmark comeback victory against Brazil in last year's World Cup.
"Even when they scored their third goal, there was something in me that berkeley north face outlet knew that we had more, that we could give more," Wambach said. "I don't know what that means, quite honestly. I don't know if it's just confidence until the end, but this team has a belief in itself, even when the going gets rough."
Next comes the game the US players have been eyeing for more than a year, a rematch with Japan on Thursday at Wembley Stadium with gold on the line. The topranked Americans lost to Japan on penalty kicks in the World Cup final last summer, a stunning blow that became a source of motivation as the players prepared for this year's Olympics.
"This is redemption for us," midfielder the north face outlet online Carli Lloyd said. "We know how hard it was for us after that game. It hurt us for a really long time."
The US team has played in the title match in every Summer Games since women's soccer was introduced in Atlanta in 1996, winning the gold in 1996, 2004 and 2008 and the silver in 2000.
The Americans advanced by continuing its dominance of the neighbor to the north, extending its unbeaten streak against Canada to 27 games (2304). The Americans lead the alltime series 4435, the last loss coming at the Algarve Cup in 2001.
But it wasn't easy. Sinclair was an imposing force, scoring her 141st, 142nd and 143rd goals in international play. She's even with Wambach for No. 2 on the alltime list, both chasing Mia Hamm's world record of 158.
Canada coach John Herdman said before the game that the run of futility against the Americans was on the minds of his players, and he addressed it with them in the runup to the match. He also injected some pregame intrigue by accusing the Americans of using "highly illegal," overly physical tactics on free kicks and corner kicks.
Certainly, his team gave one of its most spirited efforts on the biggest stage ever for a game between the neighboring rivals, scoring the most goals the US has allowed since a 54 win by the Americans over Australia in May 2008.
The game included a pair of US goals resulting from moments rarely seen in soccer, including a corner kick that curled in for a goal and a goalkeeper whistled for holding the ball too long. Canada coach John Herdman felt the goalkeeper call was a miscarriage of justice, and he felt referee Christiana Pedersen of Norway missed a hand ball in the penalty in front of the US goal.
"She will have to sleep in bed tonight after watching the replays," Herdman said. "She's gonna have to live with that. We will move on from this. I wonder if she will be able to."
The Americans dominated possession in the early minutes, but then the US defense did the unexplainable it lost track of one of the top goalscorers of all time.
MarieEve Nault played a ball ahead to Melissa Tancredi, who tapped a pass over to Sinclair. Sinclair then slalomed through the penalty area, maneuvering around defender Kelley O'Hara to beat goalkeeper Hope Solo with simple rightfooter from 10 yards.
It was the first goal allowed by the US in more the 360 minutes, since a pair of early scores by France in the Olympic opener two weeks ago. The US also trailed at halftime for the first time in this tournament.
The Americans found an unconventional way to pull even early in the second half, with Rapinoe scoring directly on a corner kick. She curled the ball just inside the near post, glancing off the legs of defender Lauren Sesselmann and goalkeeper McLeod as it settled in the net.
Then came a dizzying sequence of three goals in six minutes. The TancrediSinclair combo worked again, with Sinclair heading Tancredi's cross just inside the post from 10 yards to put Canada ahead 21. Three minutes later, Rapinoe got her second, launching a rightfooter from the edge of the area and off the post.
Then it was Tancredi again, leaping high to head in a corner kick, again just inside the post for goal No. 143, moving her temporarily ahead of Wambach.
Wambach got even with Sinclair and tied the game with a penalty kick resulting from an unusual call: McLeod was whistled for holding the ball more than six seconds, giving the Americans an indirect free kick inside the area. Rapinoe took the kick, and it glanced off the arm of Nault. The referee awarded the spot kick, which Wambach converted off the left post in the 80th minute.
The game became a battle of attrition in extra time, with the Americans having the better of the chances. Wambach put a header off the crossbar in the 119th minute. The officials then declared there would be three minutes of injury time, just enough for Morgan to put one in and avoid the penalty kick shootout that Solo was already preparing to face.
"I don't have much to say because I need to wrap my head around what just happened," Solo said. "And that's the truth of the matter. We tend to keep things interesting."