OMAHA, Neb. — Cullen Jones rocketed to an American record in the 50-meter freestyle preliminaries at the U.S. Olympic swimming trials on the Fourth of July.

Jones touched in 21.59 seconds, lowering the old mark of 21.76 set by Gary Hall Jr. at the 2000 trials. Jones gulped one breath halfway through Friday's chaotic race.

"I'll take an American record," he said, smiling. "I definitely put my head down when I was going into the wall, but I think there's a lot more in the tank."

He, Ben Wildman-Tobriner and Hall were the only men under 22 seconds in the morning heats. World champion Wildman-Tobriner qualified second in 21.68; Hall, the 33-year-old, two-time defending Olympic champion, was third in 21.89.

"Everybody anticipated that record was going down," Hall said. "There's just been too much fast swimming in the world. Records don't last, especially these days."

Jones was the silver medalist at last year's world meet, where Wildman-Tobriner was the surprising winner. But Jones has struggled to regain the form he first showed in 2006, when he became the first black swimmer to break a world record on the victorious 400 free relay at the Pan Pacific Championships.

"There's a lot of things that go into the 50 freestyle," Jones said. "One of the things is you have to be perfect for the most part or at least try to. There's never the perfect race, you always mess up something. That's what I love about the sport. You never swim that perfect race, but you keep trying."

Nathan Adrian, 100 free champion Garrett Weber-Gale and 100 free runner-up Jason Lezak all tied for fourth at 22.05.

Also advancing to the evening semifinals were 100 backstroke runner-up Matt Grevers, Nick Brunelli, 2004 Olympian Gabe Woodward and two-time Olympian Neil Walker, who like Lezak, is 32.

Jones was third and Adrian fourth in Thursday's 100 free, both earning their first Olympic berths as relay swimmers. Jones' mind was racing later that night.

"I sat up in my bed just daydreaming about how I was going to swim the 50," he said. "I just kind of slapped myself and said, 'Wait a minute, you have to sleep before you can do that.' I had to force myself to go to sleep."

Ian Crocker and Michael Phelps set up another of their eagerly awaited matchups in the 100 butterfly by posting the two fastest prelim times.

Crocker, who set the world record three years ago, hit the wall in 51.52 — the only man under 52 seconds.

He's been waiting to swim since Wednesday, when he was disqualified for a false start in the 100 free prelims, similar to what happened in a relay at last year's world championships.

"I've been in the hotel watching people do amazing things, and I've been waiting around for my shot," Crocker said, insisting he feels no extra pressure having only one chance to make his third Olympic team.

"The 100 fly was the gift I was given, and you shake your moneymaker and see what happens," he said.

Phelps touched in 52.21. He rarely bothers to check out other heats, but this time the world champion stopped downstairs to watch Crocker's swim on TV, then bent over to get a glimpse of his rival's time on the arena scoreboard.

"I was just seeing what everyone went," he said with a goofy grin. "Crocker, Davis (Tarwater)."

Two-time world champion Kate Ziegler topped Katie Hoff in qualifying for the 800 free, winning her heat in 8 minutes, 29.39 seconds to set up their second showdown of the meet in Saturday's final.

Hoff finished in 8:29.91. She's already qualified for four individual events and one relay, while Ziegler got on the team as runner-up to Hoff in the 400 free.

"The 800 is one of my favorite events. I want to do well," Ziegler said. "It should be a good race. Hopefully, we can push each other to some good times."

As expected, Hoff dropped out of the 200 backstroke prelims later in the morning. She had entered it only as a backup event.

Elizabeth Beisel, a 15-year-old from Rhode Island, was the leading qualifier in 2:07.44, bettering the trials record from 1992. She's already on the team, having finished second to Hoff in the 400 individual medley.

Beisel's time was third-best in the world this year and would have won the gold medal by 1.75 seconds four years ago in Athens.

Hayley McGregory was second-quickest in 2:07.76, three days after she briefly held the 100 back world record and then failed to qualify for Beijing. She was third in the final behind Natalie Coughlin and Margaret Hoelzer, who was third-fastest Friday.

"To finish third at a meet like this is incredible. When you look at it that way instead of the other way, it's not that disappointing," she said. "I just want to make the team. It doesn't matter if it's the 100 or the 200, I just want to be there."