INDIANAPOLIS — Four months after deciding to keep swimming, Michael Phelps took ownership of a world record that had eluded him for years.

He won the 100-meter butterfly at the U.S. national championships Thursday night in 50.22 seconds, lowering Ian Crocker’s mark of 50.40 set at the 2005 world championships in Montreal.

Phelps’ feat came just two months after returning from a suspension that was part of the longest layoff of his career, which he considered ending when a photograph of him using a marijuana pipe surfaced.

“It really shows anything can happen if you put your mind to it,” Phelps said. “It feels good to get a best time.”

Wearing his usual Speedo LZR suit, Phelps led at 50 meters with a split of 23.83, just three-tenths off world-record pace. Known for his strong finishes, the 14-time Olympic gold medalist pulled clear down the stretch to beat Tyler McGill, who touched in 51.06. Aaron Peirsol was third in 51.30.

“Crock had a ton more first 50 speed than I did. That’s something I’ve really been working on,” Phelps said. “I’ve always been able to come home pretty strong. I finally got the front half a little bit faster. If I can get that even faster, I’ll be in better shape.”

Phelps currently holds individual world records in the 100 and 200 flys, 200 and 400 individual medleys, and the 200 free.

“They’ve all been absolutely incredible,” he said.

Phelps had owned the 100 fly mark for a day at the 2003 world meet in Barcelona. But Crocker took it from him a day later, then lowered it twice more, something that has bugged Phelps ever since.

“To finally be able to get it tonight means a lot,” he said.

Phelps was in the 100 fly final when Crocker broke the record in Montreal.

“That is the worst Michael has ever gotten beat,” his coach Bob Bowman said.

Last month, Phelps came close to claiming the mark when he won the event at a meet in Montreal with a then-personal-best of 50.48.

“Crock actually texted me after and wished me all the luck and telling me that was my record,” he said. “That meant a lot, from a competitor and a friend and a classy guy. We had amazing battles back and forth. Those are something I definitely miss.”

Crocker hasn’t swum competitively since losing the 100 fly to Phelps at the Bejing Olympics, where Phelps won a record eight gold medals.

Phelps’ victory gave him a spot in the event at the world championships later this month in Rome. He already qualified in the 200 fly and 200 freestyle as he continues his transformation from swimming middle distances to sprints.

“We’ve been trying to get his stroke a little flatter and with maybe a slightly higher tempo,” Bowman said. “He sensed he was in condition to break the record.”

His success comes after a rocky post-Olympic period in which the 24-year-old superstar took a six-month break, gained 20 pounds, and the marijuana pipe photo surfaced, resulting in a three-month suspension by USA Swimming. That ended in early May and then Phelps lost some races while preparing for nationals.

“I wasn’t sure he would break any records this year,” Bowman said.

Dara Torres is also going to Rome, having won the 50 free at age 42 despite an ailing left knee that has a torn tendon and arthritis. She plans to have surgery later this summer.

Wearing a Jaked suit, Torres clocked 24.43, well off her American record of 24.07 set at the Beijing Olympics, where she won three silver medals as a hero to weekend warriors everywhere. It will be her first appearance at world championships since 1986.

“It’s a great feeling to be able to come out here and still race, but that time won’t medal at the world championships,” she said. “I guess I really don’t think about the age thing until I get out of the pool and I’m limping with my knee.”

She beat a field of women who weren’t yet born when Torres competed in the first of five Olympics in 1984. Olympian Amanda Weir took the second spot in 24.70.

“The adrenaline kind of comes, so you don’t really think about it once you get off the blocks,” she said about her knee. “Obviously, it had an impact on my start because I was so slow.”

Olympian Nathan Adrian won the men’s 50 in 21.52, but he wasn’t the fastest man in the pool.

Cesar Cielo of Brazil clocked 21.14 to win the ‘B’ final, where he and Fred Bousquet of France were relegated because only Americans are allowed in the ‘A’ final. Bousquet, the world recordholder, finished second in 21.36. Their times — the fastest ever on American soil — would have put them 1-2 in the event.

Olympic teammates Cullen Jones, who qualified fastest, and Garrett Weber-Gale tied for second in 21.55 in the ‘A’ final, setting up a swim-off on Saturday.

Elizabeth Beisel qualified for her first world championships at 16 with a victory in the 400 individual medley. She finished in 4:36.31 and Julia Smit, already on the U.S. team, was second.

Dagny Knutson, a promising 17-year-old from North Dakota, came up short with a third-place finish. She has one more chance at making the world championships in the 100 free.

Rebecca Soni, the Olympic silver medalist, won the 100 breaststroke in an American-record time of 1:05.34. She erased the mark of 1:06.20 set by Jessica Hardy at the 2005 world championships.