RIO DE JANEIRO — Michael Phelps has to clear out more space in his medal case.

Time to make room for gold No. 19.

With yet another dazzling performance, the most decorated athlete in Olympic history added to his staggering haul Sunday night in the 4×100-meter freestyle relay, giving the United States a lead it never relinquished.

Defending Olympic champion France was leading when Phelps dove into the water on the second leg, taking over for leadoff swimmer Caeleb Dressel. Even though the 100 free isn’t one of his specialties – he’s never swam it at the Olympics – he blazed down and back in a stunning 47.12 seconds, a time that was faster than all but the three anchors on the medal-winning teams, three of the best in the world at that distance.

Ryan Held protected the lead before giving way for Nathan Adrian, America’s best sprinter.

At that point, it wasn’t really in doubt.

Michael Phelps, front, and Caeleb Dressel celebrate after their team won the gold medal in the men's 4x100-meter freestyle Sunday. It was the 19th gold medal and 23rd medal overall for Phelps – the most decorated athlete in Olympic history.

Michael Phelps, front, and Caeleb Dressel celebrate after their team won the gold medal in the men’s 4×100-meter freestyle Sunday. It was the 19th gold medal and 23rd medal overall for Phelps – the most decorated athlete in Olympic history. Associated Press Associated Press/Martin Meissner

But Phelps wasn’t taking any chances, pounding the starting block and shouting toward Adrian as the anchor made the turn for home.

When Adrian touched the wall first, posting a winning time of 3 minutes, 9.92 seconds, Phelps thrust his right arm in the air and looked toward his infant son, Boomer, nuzzling in the arms of his mother, Nicole Johnson, the roaring crowd blocked out by noise-canceling headphones.

France took the silver in 3:10.53, while Australia claimed the bronze in 3:11.37, holding off a Russian team that was booed during the introductions – a reminder of the drug scandal that has rocked the nation. Vladimir Morozov, initially banned from the Olympics, was one of Russia’s relay swimmers.

It was quite a night for the Americans.

Racing nothing but the clock, Katie Ledecky gave the U.S. its first victory by crushing her own world record in the 400 freestyle.

The result was totally expected. The unassuming teenager from suburban Washington has dominated the longer freestyle events since winning gold in the 800 free at the London Olympics as a 15-year-old.

The only drama was whether she’d take the world record even lower.

Her powerful stroke quickly made that a moot point, too.

Ledecky kicked off the first wall with a lead of nearly a body length and steadily pulled away from the overmatched field – as well as the world-record line superimposed on the video screen.

Her arms churning effortlessly through the water, Ledecky touched nearly 5 seconds ahead of her closest pursuer and quickly whipped around to look at the scoreboard.

When Ledecky saw the time – 3:56.46 – she let out an uncharacteristic scream and shook her right fist. She crushed the mark of 3:58.37 that she set nearly two years ago.

“I was pumped,” Ledecky said. “That’s what I wanted and I had been so close to breaking that all year, the past two years. I knew I was due for a breakthrough.”

Ledecky, who added gold to the silver she won in the women’s 4×100 free relay, is also favored in two other individual events: the 200 and 800 free. In addition, she could pick up another gold in the 4×200 free relay.