The first one came on a warm August night beneath the Athenian stars eight years ago, the 19th arrived last night beneath the signature curved roof of the Aquatics Centre and it made Michael Phelps the most decorated Olympian in history.
His 4x200m freestyle team-mates did the graft, pounding out a sizeable lead over the French, the nation who had snatched away US gold two nights earlier, and then Phelps did the rest. Behind him was Yannick Agnel, two freestyle golds to his name already, but there was no catching the greatest Olympian.
"I did start to smile when there were 20-25 metres to go," said Phelps. "It was a cool feeling. I set myself a goal of doing something no-one had ever done before and there was no way I was going to be stopped."
Phelps touched home to the loudest roar of the week. His own moment of history came as part of a team, a fitting finale for someone - still at 27 a young man - who for all the gold that hangs around his neck has never presented himself as anything other than a team man, in fact rarely presented himself as anything other than an easy-going boy from Baltimore. He has brought back episodes of The Wire with him to London to kill time in the athletes' village in between swims.
He now has three more Olympic medals to add to the 16 back home. That makes 19 and that is one more than Larisa Latynina, the Soviet gymnast who won nine golds, five silver and four bronze over the course of three Games from 1956. Fifteen of Phelps are gold.
Medal No 18 had arrived an hour earlier in the 200m butterfly but not as expected and in a manner that stirred a rare display of anger. The 200 fly is his signature event. This was supposed to have been his third successive triumph and he led from start until the final desperate reach for the finish when the 20-year-old South African Chad le Clos stretched to collect his very first Olympic medal.
It was another silver for Phelps, the second of this Games. He tore off his swim cap and threw it back down the lane. It was a night of curious contrasts, greatness mixed with another hint the power is finally fading.
Phelps is a human designed for the water. He is tall, 6ft 4in, but not outstandingly so in comparison to his rivals. There are instead two peculiarities; his wingspan, all 6ft 7in of it, and his body shape. He has proportionately short legs and a long torso, the ideal build for the dolphin kick, the power behind his path to the throne.
That opening night in the open-air pool in Athens had seen him lay down a monumental marker; a first Olympic gold collected in world-record time. It came in the 400m individual medley, the race that on Saturday had suggested the imminent arrival of mortality. "Horrible" was how Phelps described his first swim as he scraped into the final by 0.07sec. He never featured as Ryan Lochte surged to gold and the doubts that accompanied him over the Atlantic bubbled to the surface of the Aquatics Centre.
Ever since he hauled himself out of the water in Beijing four years ago his commitment to a sport that has been his life since the age of nine has been questioned. He went home and enjoyed himself, a 23-year-old relishing the trappings of fame and fortune - his achievements were well rewarded. First stop was Caesars Palace in Las Vegas - where he crossed paths with the British rower Mark Hunter.
Hunter struggled for a time to find a way ahead after his gold in Beijing; many athletes talk of an emptiness once it is all done, four years of tough, physical, relentless grind followed by a flash of glory. And then what? For Phelps it was a problem magnified. He had 14 gold medals hanging around his neck.
But just as it is difficult to do, so it is even harder to let go. Phelps's results since Beijing - when he shed the extra pounds and dived back into the pool - are difficult to read. He won four gold at the world championship but - and that's the issue with Phelps version 2012 he comes with a but - it wasn't Phelps mark 2008.
Phelps's swims in London have been equally confusing. The horrors of the 400m IM on Saturday were followed by an explosive leg in the 4x100m relay while in the heats and semis for the 200m fly he managed to look both good and bad in the same race. Last night was much the same but shortly before 9pm that mattered not a jot.
"There were," he confessed afterwards, "so many emotions on the podium I couldn't even sing the anthem."