Britain's athletes won six gold medals Saturday, touching off waves of revelry around the city.
Feats of excellence abounded, particularly from Serena Williams on the tennis court but also from a man running on artificial legs and from two triathletes who almost finished in a dead heat after 2 hours of swimming, cycling and running.
Nevertheless, the largest spotlight of all was focused on the man who has been in it ever since he arrived in London.
When the 2008 Olympics began in Beijing, the record for most gold medals in a career was nine.
In a relatively short period of time, their record has been buried.
Phelps ended his Olympic career Saturday by winning his 18th gold medal. He did so in the 400-meter medley relay, moving into first place during the butterfly leg and then handing things over to freestyle specialist Nathan Adrian to finish up.
After swimming in four Olympics, Phelps has sworn this will be his last. He clearly has nothing left to prove.
His 22 overall medals is the Olympic record by four.
Phelps and his American teammates closed out the Olympic swimming program with 30 medal-winning performances. One of them came from the women's medley relay Saturday, where individual champions Missy Franklin, Rebecca Soni, Dana Vollmer and Allison Schmitt teamed up to break the world record.
There were 25 medal events held Saturday, most thus far in London, and somewhat remarkably the United States and China produced the same number of gold medal efforts (five). They also won the same number of overall medals (11). That left the Americans one in front of the Chinese in victories (26 to 25) and total medals (54 to 53).
The Americans and Chinese and all the others, however, had a hard time matching the enthusiasm of the British team because it was a huge day for the home side.
Team Great Britain won two gold medals in rowing, another in cycling and an astonishing three in track and field. Mo Farrah won the first Olympic 10,000-meter run in history for Britain, Greg Rutherford gave the British a long jump win for the first time in 48 years and Jessica Ennis crushed the competition in the heptathlon.
Ethiopians had won the last four 10,000-meter events at the Olympics, but not only did Farrah sweep past the medal hopefuls from that country, American Galen Rupp did as well. Rupp's silver medal in the race was the first for the United States since the Tokyo Olympics in 1964.
Earlier in the day, South African Oscar Pistorius ran in the opening qualifying heat of the 400-meter run and his second-place finish earned him a spot in Sunday's semifinals.
Pistorius was less than a year old when his legs were amputated between the knees and ankles, and he keeps up with fellow world-class runners on limbs made of carbon fiber. He faces an uphill battle to make the finals, but he has climbed tougher mountains.
During the morning hours, women triathlon competitors battled for a gold medal -- and it turned out to be a battle, indeed.
Four of them were still in a pack as they neared the finish, but Nicola Sprig of Switzerland and Lisa Norden of Sweden inched in front of the other two.
After 1 hour and 59 minutes of giving it their all, they sprinted stride for stride to the line. The clock said they covered the distance in the same time. The photo said Sprig had won by an eyelash, which they were told as they were sprawled on the pavement completely exhausted.
One of the American gold medals Saturday came from Williams, who has won five Australian Opens, one French Opens, five Wimbledon titles, three U.S. Open crowns and now one Olympic gold singles medal.
She breezed past Maria Sharapova 6-0, 6-1 to do it and now will try to win the doubles title with her sister Venus -- something they did four years ago in Beijing and in 2000 in Sydney.