London (CNN) -- She didn't even know she had produced one of the most dramatic goals in U.S. women's football history until the crowd and her teammates went crazy.
With the match between the United States and Canada just seconds from going to penalty kicks, American Alex Morgan outleaped a Canadian defender and headed a Heather O'Reilly cross over goalkeeper Erin McLeod to give the U.S. a thrilling 4-3 extra time victory on Monday.
"I didn't even see it go in," Morgan said. "I just try and be in the right position."
Three times, the Canadians took a one-goal lead, as their star Christine Sinclair scored in the 22nd, 67th and 73rd minutes. But Megan Rapinoe of the U.S. netted twice and Abby Wambach scored a penalty kick after a disputed call to send the match into extra time.
"We are unwilling to give up and that says a lot about who we are as a team, what our goals are," Wambach said. "Even when Canada scored their third goal there was something in me that knew that we had more, that we could give more. I know that this team has belief in itself, even when the going gets tough."
The Canadian players said the referee helped the U.S. win.
"She actually giggled (when awarding the penalty) and said nothing," Sinclair said. "Classy! In an important match it's a disappointment that the referee had such an impact on it. We feel cheated."
The U.S. will meet World Cup winners Japan in Thursday's final at Wembley Stadium, a rematch of last year's Cup final in which Japan won the penalty-kick shootout 3-1.
The Americans have won three of the four previous gold medal matches. At Beijing, the U.S. beat Brazil 1-0 on an extra time goal.
The U.S. men's basketball team pulled away from Argentina in the third quarter and won 126-97 to set up a quarterfinal match against Australia, which finished fourth in its group.
Kevin Durant led the Americans with 28 points. LeBron James had 18, including the first seven U.S. points of the third quarter. The Americans only led 60-59 at halftime, but outscored the Argentines 42-17 in the third period.
While the Olympics continue for Team USA and the American women, a legend's career has come to an end.
Michael Phelps, the most decorated Olympian in history, said Monday that he really means it when he says he is retiring.
"I'm done. I don't know if people really believe me, but I am actually finished. I'm retiring," he told CNN's Becky Anderson.
"D-O-N-E. Done," she pressed.
"Yes -- I'm done," he insisted.
Phelps, the U.S. swimmer, not only shattered the record for the most medals ever won by a single person at the Olympics -- with 22, including 18 golds -- but also made history as the first swimmer to win gold in two different events in three consecutive Olympics.
On Monday, he also defended the gold medal-winning swimmer Ye Shiwen, who has been suspected -- without proof -- of doping after her remarkable victories.
"It's kind of sad that people have a great swim and that's the first thing they say," Phelps said of the Chinese 16-year-old.
"People who work hard -- it shows. There are people who just jump to that conclusion sometimes, and it's not right."
American gold medal gymnast Gabby Douglas was back in action Monday on the uneven bars, but turned in a disappointing performance and came eighth.
"It was an amazing finals with so many great competitors," she said. "Coming into bar finals was a big challenge for me, and I made a little mistake. Even if I would have hit a solid routine, I know I have a lower start value than the other competitors."
Hometown favorite Beth Tweddle took bronze in the event, behind Russia's Aliya Mustafina, who claimed gold, and Kexin He of China, who earned silver.
"I'm very happy that I'm following on with the Russian traditions," Mustafina said. "When I won the bronze medal (in the all around), I became more confident that I could overcome my (2011 ACL) injury and do better."
At Olympic Stadium, site of track and field events, Jennifer Suhr of the United States cleared 4.75 meters (15 feet, 7 inches) to win the women's pole vault. Silver medalist Yarisley Silva of Cuba cleared the same height but had more misses in the competition than Suhr.
Two-time champion Elena Isinbaeva of Russia was third.
"It's something that's so emotional I can't even describe it," Suhr said. "To work so hard for four years, to have injuries. My husband (and coach) and I got through this. To have faith and to have it all come together and to achieve what we dreamed of, it's amazing."
Kirani James of Grenada won the men's 400 meters and gave Grenada, which competed in its first Olympics in 1984, its first medal ever.
The 19-year-old thanked God, his coach and his family.
Of his family he said: "They're probably having a street party; everyone's having a good time."
In the 400-meter hurdles, Felix Sanchez of the Dominican Republic, with a picture of his late grandmother underneath his name bib, won the gold medal, fulfilling a promise he made after he learned she had died while he was racing at the 2008 Olympics.
"When I got on the podium it was raining and it was as if my grandmother was crying tears of happiness, crying for all the sacrifices I have made," he said.
Pavlos Kontides earned the first medal for Cyprus ever -- a silver -- in the Laser class sailing competition.
"It is really amazing. For me and my country, it is a historic day," he said. "I suspect my name will be written in golden letters in Cyprus."
It was another tense final shot, and another awful one for American Matt Emmons but he still managed to finally get a medal in the men's 50-meter rifle three positions.
Going into the last round, Emmons sat in second. He had to be thinking about the previous two Games when he was in gold-medal position with one shot to go. But each time before he had blown it, once shooting at the wrong target and once his rifle went off before he had lined it up with the target. Those times he not only lost gold, he lost any medal.
This time, he scored 7.6 on his final shot, his worst score of the day, but it was enough to stay ahead of Cyril Graff of France for a bronze.
"Any time you stand on an Olympic podium is not a loss, it is a pretty cool thing," Emmons said.
His wife, a shooter whom he met after his disappointment in Athens, said her husband was extremely nervous before the final shot.
"He couldn't hold still, so he just took the shot as best he could," Katy Emmons said. "This time the luck was on his side."
It was a sixth medal for the family -- Katy has three for the Czech Republic and Matt has previously won a gold and a silver medal in the 50-meter prone event.
A gold medalist found himself at the center of another controversy Monday as Kenyan police confirmed that steeplechase winner Ezekiel Kemboi was under investigation on suspicion of trying to stab a woman on a date before he left for the Games.
The woman accused Kemboi of making sexual advances, said deputy police spokesman Charles Owino, without naming the alleged victim. Kemboi is a police officer himself, according to Owino.
Kemboi said that he was the victim of attempted extortion and that police had not given him a fair hearing, Owino said.
And the International Olympic Committee announced that it disqualified American judoka Nicholas Delpopolo from the men's 73-kg judo event for a doping violation. It stripped the 23-year-old of his seventh-place finish after he tested positive for a cannabis byproduct.
CNN's Jo Shelley and Bharati Naik contributed to this report.