It belonged, though, to American Ian Crocker, who set the mark in 2005 in a race in which he beat Phelps by more than a second. The memory still makes Phelps furious, and Crocker's record, until Thursday night, had remained out of Phelps' reach.
But Phelps finally got it, touching the wall at the Indiana University Natatorium in a stunning 50.22 seconds. It was the highlight of another exciting night at the U.S. nationals, one that also saw Dara Torres make the world championships team in the 50-meter freestyle at age 42.
After touching the wall, Phelps whipped off his goggles, yanked off his two swim caps, shook the water from his face and glared up at his time. It took 15 seconds before he smiled, but the look on his face revealed an unmistakable truth: He expected to grab this record. And now he finally had.
"This is something that I really, really wanted to accomplish," Phelps said. "Crock and I had a lot of great history, a lot of great races with one another. I've wanted that record ever since he took it in '03 worlds. ... After the race, you could tell I was pretty fired up and excited."
Phelps owns five individual world records: the 100 butterfly, the 200 butterfly, the 200 freestyle, the 200 individual medley and the 400 individual medley. No other person in the world, man or woman, has more than two. He also was a member of three American relay reams that hold world records.
"Everything I've done is something I've wanted to do and something I've dreamed of," the Baltimorean said. "I will say, I would have liked to have gone 8-for-8 in Beijing, but it feels good to have that one. Looking back at some of the things I've done, it's just been incredible."
Phelps paid tribute to Crocker several times after the race. For years, their duels were among the most exciting in swimming. A movie, Unfiltered, was made about their rivalry. At the 2003 world championships in Barcelona, Spain, Phelps grabbed the world record in the 100-meter butterfly for the first time (51.47) in the semifinals, but Crocker took it away the next night (50.98). At the 2005 world championships in Montreal, Crocker handed Phelps the worst defeat of his career, finishing in 50.40 while Phelps went 51.65.
"Honestly, in the race where Ian broke the record, that is the worst that Michael has ever been beaten," said Phelps' coach, Bob Bowman. "I remember Michael got out [of the pool] and said, 'What happened? I want to put a bag over my head.' I said, 'Me, too. Let's get out of here.' That was an amazing record, and that's why it stood the test of time."
Failure, though, has always motivated Phelps more than success. He carried that defeat with him for years, but it wasn't until he decided he wanted to focus on the shorter events that he felt as if he could train like a sprinter. For the past five months, he's been working hard in the weight room, trying to become more explosive. His first 50 meters, he was behind Crocker's world-record pace, but it was the fastest split of Phelps' career (28.23).
"It kills my body. It's killed me over the last few months," Phelps said of his increased focus on weight training. "There are days when I can't pick anything up, I'm so dead from doing it. But I guess some of it is working."
Crocker, who retired after the Beijing Olympics, recently sent Phelps a text message wishing him luck and telling his old rival he wanted him to break the record.
"That meant a lot from a competitor, a friend and a classy guy," Phelps said. "He and I had amazing battles back and forth, and those are something I'll definitely miss."
If you can believe it, neither Phelps nor Bowman thought it was a perfect race. Might we see Phelps break the 50-second barrier in two weeks at the world championships in Rome?
"I'm hoping with a couple more weeks, he'll get faster," Bowman said. "He needs to hit the turn better. He kind of messed up the turn, and if he hits that, he can go a really good time."
Phelps conceded that he had extra motivation for this race besides chasing Crocker's mark, but he refused to say what it is.
"It's going to be extra motivation for quite some time," Phelps said. "It will be something that will be burning inside me and firing me up for months."
Phelps' motivation might have something to do with the recent swimsuit controversy caused by FINA's decision to allow nearly any suit on the market to be worn in competition, despite questions about how much they contribute to an athlete's performance. Phelps has refused to address swimsuit questions all week, and the fact that he broke this world record in a Speedo LZR Racer when a lot of swimmers are wearing suits that might be banned in 2010 seemed to give him extra satisfaction.
"We've been really excited about wearing the Speedo suit," Bowman said dryly. "That really helped."
Torres was wearing one of the new suits made by the Italian company Jaked when she won the 50-meter freestyle, but she wasn't thrilled with her time (24.43).
"My coach was telling me I probably lost four or five tenths [of a second] on the start," said Torres, who has been swimming despite a knee injury. "The adrenaline kind of took over, so I didn't really feel it."
To put their accomplishments into perspective, consider this: Torres won her first national championship in 1982. Phelps was born three years later.
"It's a great feeling to be able to be out there and still race, but that time won't medal at the world championships," Torres said.
Towson's Katie Hoff on Thursday pulled out of the 100-meter and 800-meter freestyle events, ending her nationals. She did not make the U.S. team that will compete in Rome at the end of the month.